Notes on the Construction and Equipment of Trenches

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BOX ASSXFlOATION C

NOTES ON T H ECONSTRUCTION AND EQUIPMENTOF TRENCHES

C O M P I L E D IfR O M T H E L AT ES T S O UR C E SA RM Y WAR C OLLE GE

APRIL,1917

WASHINGTONGOV ER N MEN T P R IN T IN G OFF IC E

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THEJ GENERAL SERVICE SCHOOLSLIBRARY

K 914D3 B15C L A S S N UM BE R .1A C CE SS IO N N U M B E R


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CONFIDENTIAL IFOR OFFICIAL USE ONLY

NOTES ON THECONSTRUCTION ANDEQUIPMENT

OF TRENCHES

C O M PIL E D F R OM THE L A T ES T S O UR C ES ARMY WAR COLLEGE

APRIL,1917

WASHINGTONG O VERNMENT PRINTING O FFICE

1917


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W A R D E P A R TM E N T ,D O C UM E N T N O . 592.Officeof The A djutant General.


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WAR DEPARTMENT,WASHINGTON, May 16, 1917.The following Notes on the Construction and Equ ipment ofTrenchesarepublished forth einformation ofall concerned.

[2602979,A.G.O.]B Y ORDER OFTHE SECRETARY OF W AR :

T A SK E R H . B L IS S ,MajorGeneral, Acting Chiefof Staff.OFFICIAL:

H. P. McCAIN,TheAdjutantGeneral.


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CONTENTS.Trench terminology 1-8Moderndevelopments 1-3Intrenched zone,description and details 4-19Supportingpointsdescribedandillustrated, PlatesI andI I . 20-24Additionalintrenched zones 25Selectionofsite,includingpreparation 28-35Profiles, filing, c ommunicating and approach trench es 38-40Traverses, classes,advantagesand disadvantagesin tren ch es. 41-42Head cover, definition andmethod ofsecuring 43Overhead cover, classes and descrip tion, including cave

shelters 4 4 ^9Revetments,necessity for, andmethods 50-57Drainageoftrenchesandshelters 58-80Latrines, location and systems 61-82Obstacles, tactical use, requisites, kinds, and constructionm ethods,including obstaclesin approachtrenches 63-72Defenseofbuildings,advantagesandmethodsofpreparation. 73Construction oftrenches, under fire, atnight, d etails 74-81Employment ofengineers 82Training in fie ld fortifications, necessity for, of troops to occupythe trenches 83Equipm ent and maintenance field fortifications, requisitesandprovisionfor 84-105Notesonfield defenses pp . 55-64Appendix I . Consolidation of trenches pp . 65-95Appendix I I . Wireentanglements p p . 97-102Plates I toV pp . 103-1085


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NOTESON THECONSTRUCTIONAND EQUIPMENTOFTRENCHES.

MODERN DEVELOPMENTS.1 Th enamefieldfortification wasoriginallyapp lied toth at class

ofmeasures taken for the defense ofpositions intended to be heldtemporarily . In the present European war, however, temporary positionsh ave often been occupied for suchlongperiodsth a t theirfortification hasacquired many ofth e characteristics of perm anentworksorsiegeworks,resultinginadevelopmentoftheartwhichweseektodescribebytheterm''trenchwarfare"or"positionwarfare.''Theprinciplesoffieldfortification orfieldintr ench m en th aven otchanged,butmanyextensions,adaptations,andnewapplicationsofexistingprincipleshavebeendevelopedintheEuropeanwar.

2 The developments to benoted are due to the following maincauses:(a) Improvement in artillery; longer ranges;heavier projectiles;highexplosiveshrills; specialuseofshell and shrapnelin demolishing earthworks and cutt ing wire entanglements; vast number ofgunsandenormousexpenditureofammunition;skillfulindirectfire.(6) Im proved m ethods of observation and com munication;balloons, airplanes;photographyfrom aircraft; telephon es; wirelesstelegraphy; motor transportation.(c) Continuousintrenched positionswith unassailableflanks.(d)Longcon tinued occupancy offieldworksat all seasonsof th eyear.(e) The construction ofintrenched positionsin localities of greatdiversity as to topography, character of soil, geology, vegetablegrowth,anddrainage.(/) Th ecloseproxim ityofthe opposinglinesoftrenche s.(g)Theuseofnewdevicesandmethodsofattacksuchasgrenades,trench mortars, poisonous gases, inflammable liqu ids, in tenseartillerybombardment,barrierfire,machinegunsingreatnumbers,and many accessories developed as the result of the continua lreactionbetweentheattackandthedefense. 7


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8 CONSTRUCTION AND EQUIPMENT OF TRENCHES.3. The mostconspicuous changestha t have resulted in field fortificationare:(a)Lessextensivefieldoffire.(b) Greater importance and corresponding greater difficulty ofconcealment, involving use of screens, dummy trenches, hiddenemplacements,andcoveredapproaches.(c) Deeperand narrower trenches.(d)Greateruseoftraversesandparadosinfiringtrenches.(e)Theuseofmanysupportandcovertrenchesgenerallyparalleltothefiringtrenchand notveryd istant therefrom.(/) More num erous com m unicating and approach trenches,

screened and defiladed, forming with the firing, cover,support, intermediate, andreservetrenches a labyrinth oftrench workknownasth e "first intrenched zon e."(g)Increaseduseofcover.(h) Provision of shelter for men in cover, support, intermediate,andreservetrenches ,andin deepunderground bombproofsor "c av eshelte rs," safe against powerful artillery fire; lesselaborate sheltersinthewallsofthe coverand support trenchesand sometimesin thefiringtrenches.(i) Extensive use of strong points and supporting points in thefirstintrenchedzone.(k) Provisionfor the defense ofthe comm unicating and approachtrenchesagainstflankattackbyhostileforcesthatmayhavebrokenthroughthefrontlines.

(?) Asecondintren che d zonesome2or3milesin rearoft hefirstzone,generallyonthereverseslopeofacrestorridge,andconnectedwith the firs t-zone trenches by sheltered approaches, natural orartificial.(m) Intrenched zonessti ll further to the rear for possible occupancy in caseofdefeat or retirement.(n) Increased use of obstacles, especially barbed-wire entanglements.(o) Increased useofminesand countermines.(p) Accessory special measures to prevent surprise and to resistspecialmethodsofattack.(q) Systematic measures to prevent confusion and going astrayoftroopsmovingin them azeoftrenches,byd ayandbyn ight, suchasguideposts,lights,maps,namesofapproaches,andshelters.(r) Rou tinem easuresof maintenance, convenience, and comfortduetothelong-continuedoccupancyofthetrenches,suchasrevetment, drainage, heating, food supply, water supply, ammunitionsupply,andsanitation.


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9ONSTRUCTION AND EQUIPMENT OF TRENCHES.G EN ER AL D ESC RIPT IO N O F AN IN TR EN CH ED ZO NE.

4 . T he "first in trench ed z o ne " includes th e foremost firingtrenchesandthecover,support,intermediate,andreservetrenches.An obstacle, continuous except for narrow passages for patrols, isin front of the firing, support, interm ediate, and reserve trenches,andbetweenstrongandsupportingpointsandapproaches.Thetrenchesmaybeentirelyinexcavation,partlyinexcavationwith a parapet, or the necessary cover may be provided entire ly above ground level by a h igh parapet. The second is the usualcombination with low parapet about 12 inches high. Wet groundorpoordrainagemayrequirethethirdtype.

The front line consistsusuallyoftwoparts, the firingtrench andthecoverandcommunicatingtrench.5. T h efiringtrenchmayeitherbeacontinuoustrenchofirregularorindented trace, traversed at suitable intervalstogive protectionfrom enfiladefireand tolocalizeth eeffect ofshellbursts, ori t mayconsistoffiringbays,T shapedor Lshapedin plan ,j utt ing forwardfromth ecoverorcommunicatingtrench . Th elatterisacontinuoustrench, affording easy la te ra l communication close beh ind thefiringpositionsandconnected w ith thematfrequent inte rva ls.6 . Th e supporttrenchesaccommodatethesupporttothegarrisonofthefiringandcovertrenches,thesupportbeingreadyforimmed ia te reinforcem ent of th e garrison. T he y are provided w ithnum erous shelters. T he cover trenches h av e num erous sm allshelters and furnish cover to the bulk of the garrison of the firingtrenchwhen temporarily withdrawn during abombardm ent, orforrestduringthedaylighthourswhenthereisnotmuchdangerofanattackby theenemy. Th esupporttrenchesareusually continuousin each supporting point and should be a second line of resistanceprotected in front by an obstacle , arranged so as not to interfere withtherapidreinforcement of thefiringtrench. They should beconnected w ith adjacent supporting po in ts b y communicatingtrenches. To escape art il lery fire directed on the front t renches,the support trenches should be not less than 50yards to the rear,and preferably about 100to 200yards. Support trenches are connected with thefront l ine by frequent approach trenches. Cover,support, intermediate, communicating, and reserve trenches maybeprepared for fir ing at certain point3for use in case the enemybreaksthefrontlineandmakesaflankattack.

7. Behind thesupporttrenchesand alsoconnected w iththem byapproach trenches lie the reserve trenches, which may consist of alineoftrenchesandofbombproofs,orcaveshelters,often formed by


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10 CONSTRUCTION AND EQUIPMENT OF TRENCHES.improvingthe coverofsomenaturalfeatures. Thereserve trenchesand sheltersare toaccommodate thebattalionreserve, whose function is tomake thelocal counter attack. The reservelinem ay be400to600yardsinrearofthefrontline.

8 . The intrenched zone may also include local trenches, such asthebombing trench, dug behind thefiringtrench within easygrenade-throwing d is tance of i t, i ts purpose being to drive out bygrenades an emeny whomay have captured the front l ine . As littrench isavery narrow trench dug off the communicating trenchesforth eaccommodation ofmenduring abom bardment; slit trenchesare1or2feetwideand7feetdeep.9. An intrenched zone is also usually provided with a seriesofworkspreparedforall-rounddefenseandsurroundedwithacontinuous obstacle, known in our service as strong points, or supportingpoints. Their object is tobreakupahostile attack that has penetratedthefrontline,preventitsfurtherdevelopment,andthusfacilitatecounterattack. Theymustcomeasasurprisetoth eenemyandshould be concealed asmuch aspossible. Thenumber on agivenfront will depend on the facilities offered by the ground for their concealment. Thegarrisonmusthold outtothe last,whateverhappenstothe restofthe line. Adjacent worksofthis kind should,ifpossible, afford m utual support tooneano ther.10 . Approachtrenchesleadtothefirstintrenchedzonefrompointsonroadsth at can bereached withouttoomuch exposure toview.Communicating trenches and approaches have the usual zigzagtracetolim itthe effect ofenfilade fire. Theyarealsoarrangedtobe

usedasdefensive trenchesand toserveasstarting points forcounterattacks in case the first-line trenches have been temporarily lost.Theyhaveafiringbanquetteatintervalsfromwhichaflankfirecanbebrought tobear upon the enemyifh eendeavorstopassovertheopenground in rearofthe firstline offiringtrenches. At intervalsalongthese trenches are placed supplies of obstacles to be quicklypulled into thetrenchtoobstruct theadvanceof anenemybythisroute. Atintervals sortiestepsareb uilt topermitthe defenderstodebouch and launch acounter attack. Afurther defensive featureis the occasional elevated platform across the trench at an angle,whereoneortwomenwithhandgrenadescanconvenientlyopposeanadvancealongthetrench.

Latrinesareprovidedinalltrenchesandmustbeinpositionseayyofaccessand protectedfrom fire. Th eyareusuallymadein Theadsattheendsofshorttrenchesleadingofffromtheapproach,communicating,cover,orsupporttrench.


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CONSTRUCTION ANDEQUIPMENT OFTRENCHES. 111 1 . Assembly points are former firing trenches which have been

organized for a stay of several days, or they are short trench elementsdug especially to hold companies during short stays, and in whichthe men can only sit down. Even the latter should contain waterbarrels and latrines, also a command post sheltered from rain, wherethe captain can make a light, open his map, and confer with hisplatoon leaders.

12. Strong points and supporting points.In every intrenchedzone there will be a certain number of points whose loss or occupation by the enemy will endanger seriously the rest of the line orweaken the defender's hold upon it. Other points particularlyfavorable for defense will also occur. Such points should receivespecial treatment so as to develop to the utmost their capabilities fordefense and to enable the troops to hold them even after the neighboring portions of the line have been lost. If the intervals betweenthese points are great, there should be small intermediate works.These works should be clearly designed to offer a protracted resistance, unsupported if necessary, to hostile attack from any direction,flank and rear as well as front.

The importance of the point to be strengthened, its position, andits nature generally determine the area to be inclosed. A largedefended work offers a less concentrated target to hostile guns andis therefore less vulnerable, but it requires a large garrison. I t isusually garrisoned by a battalion or regiment and is then called asupporting point. (Pis. I, II , and IV are for foreign units withcompanies of 200 men.)

13 . The small intermediate wTorks above referred to are generallyarranged for an all-round defense. Such a work is designed to beheld by a company or a half company and is called a strong point.This type of work should be carefully concealed and strongly constructed, or it will become a shell trap. Good bombproof cover forthe garrison should be provided within the work. The garrisonshould be kept small and the defense provided by machine guns toas great an extent as possible.

14. The largersupporting points are better defended by a systemof trenches covering a more extended area. The edges of such acenter should be provided with defenses against attacks from anydirection, these defenses consisting either of a continuous firingtrench or of isolated lengths of firing trench covering every possibleline of approach and connected with one another and with the worksin the interior of the locality by communicating and approachtrenches. Small strong points such as are described above might


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12 CONSTRUCTION A ND EQUIPM ENT OF TR EN CH ES.well form an element ofth e defenses ofth e largersupporting poin t.W ithin the defended perimeter should be shelters for the garrisonand a seriesof cover,support, and reserve trenches,and comm unicatingand approach trenches, many ofthem prepared forfiring.

In this way the in te rior is cu t up into compartments , and thescheme of defense is soorganized tha t even if the enemy succeedsin establishinghimself atsomepointin the perimeter an unbrokenfront can sti ll bepresented tohim and the defender's hold on thelocalityispractically undisturbed.Machinegunsplayanimportantpartinthedefense,andalternativ eemplacementsshouldbenumerous. Thesitingofth eemplacem en tsshould be verycarefully considered, soastodisperseth egunslaterallyand in de pth ,and willlargelygovernth egeneraldesignofthe defenses. A supporting point should not offer a concentrateda rti lle ry ta rget, and i ts reduction by bombardment should be adifficult and leng thy operation enta iling a vast expenditu re ofammunition."15. Villages of masonry construction placed in a state of defensemakethebestkindofsupportingpoint. (PI.IV.) Ifthedefenseisproperlyorganizedtheircapturehasusuallyprovedalongandcostlyoperation. Cellars with their roofs shored up and reinforced formexce llent shelters, and good communications entirely undergroundcanbe mad ebybreakingthroughfrom cellartocellar. Theorganization of the defense of a village issimilar to tha t described forasupporting point. The field of f ire for interior l ines of resistancem ust be improved wherever necessary by the thorough demolitionof buildings and th e removal orspreading of debris.16. Thesestrongpointsand supportingpointsshouldalwayshaveacontinuousobstaclearoundthem . Inaddition,anyinteriortrenchwhichmayundertheschemeofdefensebecomealineofresistanceshould also be covered by a wire entanglement.17 . U ni ty ofcommandisanimportantth inginthedefenseofoneof these works, and for this reason they should be designed for agarrisonofacompleteunit.18 . The supporting pointsmu st bewithin supportingdistanceofeacho ther; th atis ,effective infantryfirem ustbe abletoreach themiddleoftheinterval betweenadjacent centersofresistance. Theintervals are closed by dum my trenches soas todeceive both theaerialobserversand theassaultingtroopsoftheenemy. Th eattack ingforce will ultimately pushintoth eintervalsand may surroundthesupportingpoints,butitisnecessarytocapturethelatterbeforethe a t tack can passon. I t is sta ted that the power of the defense


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CONSTRUCTION AND EQUIPMENT OF TRENCHES. ISunder present conditions does not consist in hold ing the firingtrenches or even the support trenches bu t lies in the abil ity toorgftnize and launch the counter a t tack. The at tack and capture ofthefiringtrenchesisnotsodifficult withefficient artille rypreparation, bu t the holding of the captured trenches against a powerfulcounter a t tack from the l ine of t renches next further back is thekeyofsuccess.19. The commanders of sectors do not count on hold ing the irfiringtrenches in case of violent attack, bu t always have arrangements made in every de ta il for a counter a ttack . If the counterattackfailsthefinalresistanceismadeinthestrongpointsthatformthe reserve trenches of the supporting poin t. Supporting poin tshavebeenusuallythe causeoffailure ofattacksonintrenched linesin thepresent war. Theyare considered absolutely essential.2 0 . In the sketches illustrating supportingpoints the features tobe especially noted are:

PLATE I .Two companies in the firing l ine , one in support, and one in

reserve. Double lin e of tren ch es in front l in e ; d ou ble lin e oftrenchesinsupport; communicatingand covertrenchesbehind th efiringtrenchesoffirstline,supportlines,andinstrongpoints;twodistinctlinesofwireentanglement in front offirstline; th e wholesupporting point divided into two longitudinal sections, each protected in flank by wire; each longitudinal section divided transverselyintothree parts,viz,thefiringtrenches,thesupporttrenches,and the reserve trenches, each in turn completely surrounded bywireand each protected with trenches arranged forfiringfaced totherearaswellastothefront and flanks; passagesthroughth e wireofthefirstlinemade continuousthrough the twolines, b ut alwaysinthereentrants.Listeningpostsinfrontofeachfiringtrenchofthefirstline,placedbetweenthetwosystemsofwire.Machinegunsofthefirstlineinreentrants. Thoseon the flankstosweepth e intervals between this center of resistance and thoseadjacenttoit.Communicating and approach trenches provided wi th firingparapets mostlyfacing outward toward th e wire of each sectionofthesupportingpoint.


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14: CONSTRUCTION AND EQUIPMENT OF TRENCHES.PLATE I I .

2 1 . Threecompaniesinthefiringline,eachw ith one-halfi nsupport; onecompanyinreserve.Wire surrounds at least two distinct portions of each companyfront.W ireprotectsth e twoflanks of each communicating trench.Wiredividesthesupportingpointintothreedistinctportions.Passagesthroughthewireinthefrontlineareallinthereentrants.The supportingpoin tisprepared forall-round defense.The emplacements for the machine guns ofth e front line are in

reentrants to sweepth e front ofth e wire.Thecommunicatingandapproachtrenchesarearrangedforfiringthroughoutalargeportionoftheirlength.Communicating and cover trenches extend behind nearly allofthefiringtrenches.The railroad cu t and fill areno tprepared fordefense because,foronereason,theyaretoowelllocatedonthegeneralmapinpossessionoftheenemy.22 . Arrangementsm ustbem adeforreconnaisancepartiesandforattackingcolumnstodebouchconvenientlythroughopeningsinthel ine of defense protected by moA^able obstacle. These openingsmust be under the fire of the support trenches.Supporttrenchesarefrom 100to200yardsin rearofthe front-linedefenses. They arenot continuous asa rule . Their purpose is to limit the ret rea t of a fraction which may have been thrust backtemporarily from the front line and to givetime for the reservestoarriveandcounterattack.23 . Fa rther totherearisalineofstrongpointsgarrisoned bylocalreservessupportingthefiringtrenchesandthesupporttrenchesandsweeping with i ts fire all the ground in rear of the forward lines.Thesestrongpointsarelessnumerousandlessdevelopedthanthoseforward and are surrounded by obstacles. The intervals betweenstrongpointsarefilledwithobstaclesarrangedtoallowpassagesforthe debouching oftroopsin reserve when used in counter attacks;these counter at tacks may be made by the garrison of the reservetrenchesofabattalionsupportingpointorbytheregimentalreserves;thepassagesareproperly covered by fire. Abouthalf the crestsarefurnishedwithloopholesandtheotherhalfwithuncoveredparapets,whichperm itatthe mom entofassaultthemostrapid fire. Machineguns and l ight artille ry may also be used advantageously whenavailable. Itisimportanttodirectth e axisoftheloopholessothat


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CONSTRUCTION AN D EQ UIPM ENT OF TREN CH ES. 16there is no danger of firing into the adjacent supporting or strongpoints.24. Thereasonforbreakingafront orinden ting alineto provideflanking fire, isth at arifleman fires ordinarily at right anglestothecrestofhistrenchornotmorethan30oneachsideofsuchdirection.Donotcounttoomuchonobliquefire,especiallytotherightoblique,as the lat ter requires a displacement of the usual position of thesoldier.25. Intrenched zonesinrear ofthe first zone. Thesemay consistofanintrenched zone 2to 3milesin rear of the first zone, usuallybehind aprotectingridgeorcrestand connected w iththe first zonebyartificial ornatu ral comm unicationstha t furnish fairly goodconcealmentfrom theenemy'sviewandartil lery. Amore elaboratedefensemaycoverazoneinrear4to5milesdeepinwhichevery pointof tactical importance is fortified by supporting points as already described. Troopsoccupyingthesepointscanbreaku pth ea ttac kofahostile force tha t may have penetrated the front system, delay thefurther advance andfacili tate counter attack. They alsofurnish aframework onwhichby diggingtrenches connectingthe supportingpointsanewlinecanbequicklyconstructedtoholdagainstvigorousattack.Oneormoresimilar zonesmay beconstructed farther toth e rear.

SELECTION OF SITE.26 . Thefollowinggeneralrulesshouldbebornein m ind :(a) Study the strong and weak points of the position and locatethelineofthefiringtrenchwithdueregardtothetacticalrequirementsandtheeconomyofmen.(6)Thefieldoffireshouldbeeuchastoexposeanattackingenemytothefireofthedefendersinthelast200or300yardsoftheiradvance.Toinsurethistheforeground mayrequireclearing. Theexperienceof the present war indicates that the above width of the exposedforeground is ample and even a narrower belt is often considered

sufficient withtrained troops,providedi tisclearlycommanded fromthefiringpointsandisstrengthenedbyagoodobstaclewhichshouldalsobewellscreenedfrom the dis tan tviewofthe enem y.(c)concealment of the works and dispositions is of the greatestimportance.(d)Thedefendersshouldbescreenedfromtheenemy'sviewandsheltered from hisfireby natu ral orartificial coversoarranged astoafford themaxim developm ent ofrifle fire.


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16 CONSTRUCTION AND EQ UIPM ENT OF TRENCH ES.(e)T he foreground should have obstacles to detain the attackingtroopsunderfireandtobreakuptheirformations,birttheseobstaclesshouldnot afford coverforth e attacker.(/) Goodcommunicationsshould beprovided w ithin the positionandovergroundthatmaybeusedforcounterattacks.2 7 . First step.Thefirst step in the preparations is to improvethefieldoffire,bothbyclearingtheforegroundandbytakingrangestoallprominentobjects. Specialrangemarksmayalsobeplacediftimeisavailable,andthetroopsshouldbecomefamiliarwithfeaturesinfrontandtheirranges.Objectsinornearthepositionthatmightassisttheenemyinesti

matingrangesshould be removed oraltered in appearance, soastomakethemlessconspicuous.The l ine of t renches should not be placed too near unalterable features th at reveal the position of the lines or furnish good rangemarksfortheenemy.Thestrongerpointsinthe line,thatis,thosemorereadilydefended,may be villages, solidbuildings, patches oftim ber, hills, knolls,orbroken ground. Theseshould be specially prepared fordefense,asdescribed hereafter.2 8 . Firing trenches.Thefiringrenches constitute the principaldefense ofaposition, and they are laid out in irregular lines oringroups, w ith intervals, according to the character of the ground.Theincreasedimportanceofscreeningdefenseworksfromviewandfireof th e enem y's artillery tends toth e selection ofsitesfor firingtrenches behind rather than in front of the crest of a slightridge,provided a sufficiently clear field of fire can be obtained againBthostile infantry advancing in force. The main advantage of thisretired position ia that i t affords greater security against hostile a rtille ry fire. I t mu st b e remembered, however, t ha t securityagainstartilleryfireisalmostentirelyatthepresenttimeamatterofconcealment; th atis,securityagainstobservation. Ifth eenemyhas hilltops in Mapossession or can establish an artillery observerwith telescope and telephone on high ground from which he canoverlook the r idge or crest in front of our t renches, the back orretired position of the fir ing trench loses much of i ts advantage.Location of trenches in rear of crest lines should therefore includeasan important circumstance the denial of dominating ground totheenemy.

Trenches on the crest or forward slope are certainly exposed toview and bombardment, bu t the occupation ofhighgroundgivesafeelingofsuperioritytothetroopsandactsfavorablyontheirmorale.


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CONSTRUCTION A ND EQ UIPM EN T OF TR EN CH ES. 17The forward position hasalsoth ead vantage,if not toofardown th eslope, tha t the support and communicating trenchesand the worksinwhichmostofthegarrisonlivearefairlywellconcealedbehindthecrest. In offensive action the forward position offers greater facilities for observation and for the assembly of troops for the assaultclosetoth efront lineand unobserved.Specialconditionsmayjustifythedeliberatechoiceoftheretiredpositionbehind the crest. Ifadopted, arrangementsm ustb e madetodenytheenemyaccesstothecrestofthehillandtosecureitforourselves. Thefirms'trench must not be toofar down the reverseslope;50to100yardsfromthecrestlinewillusuallybefarenoughandgivesasufficientfieldoffireifmachinegunsarenumerousandwelllocated, and there must be an ample num ber ofsaps forwardtot he top to allow of continuous observation of the forward slope.W ith these precautions and readiness to deliver an imm ediate andvigorouscounterattackontheenemyifheappearsonthecrest,theretired position may sometimes be taken up when conditions imposeatemporarilydefensiveattitudeandlocalsuperiorityinartillery is wi th the enemy. But if the two lines remain facing each other onth esameground fora protracted period i t will beimpossibletop reven t th e enemy from ultimately establishinghimself onthecrest unless i t is included in our l ine . The location selectedshould be such as to conceal and shelter the defender's reservesand communications.

2 9 . Thesoldier,inattack,firstlearnstomakeuseofexisting coverand then to improve same when there is t ime . Where he has toadvance over ground devoid ofcoverand ishalted byth e enemy'sfirehewillh avetom ake for himself individ ual coverasrapidly aspossible,usinghisintrenchingtool. W iththishem aymakeashallowrifle pit in which he can lie, the earth thrown up in front protectinghisheadand shoulderswhilefiring.If compelled tohold the l ine wherehe has been halted, he mayimprove th is rifle p i t to a kneeling, s itting , or s tanding t rench .These individual shelters may be then connected and finally anintrenched zonedevelopsfrom thefirstseriesofsimplep its. Someofthefirstpositionsin th ewesternEuropearenawerethusoccupied ,andbysuccessiveeffortsofeachridetogetbettergroundtheyweregradually altered until an equilibrium was fairly established andthemorepermanentlineselaborated.The location is often determined under these circumstances bythe line at which the troopsare forced to halt by the enem y'sfireandtodigthemselvesin.

99454"17 2


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18 CONSTRUCTION AND EQUIPMENT OF TRENCHES.This line may in some cases be a hostile trench captured in thecourse of the attack.Smalladjustmentsofpositionmaybemadebytheofficerswithaview togettingthe best line possible under the circumstances, bu t

themenasarule startat oncetoget whatcoverthey can withthein trenching tool. Officers with the front lines should s tudy theground ahead ofthe m at every opportunity and endeavor torecognizetheminorfeaturesofrealtacticalimportance. Generally,ifth echeckismerelytemporaryanditisintendedtoresumetheadvanceat the earliest possiblemoment, allground gained should be heldexcept for very minor adjustments, unless some portion is clearlyuntenable against counter attack; if, however,strategic or tacticalconsiderations require a temporary abandonment of the forwardmovement and the construction ofa defensive line to be held forsome time, the decision will begoverned to a great extent by thesameconsiderationsasalreadydiscussedintakingupalinedeliberately, and it may be advisable to give up ground on somepartsofthe front.The s it ing and construction of a t rench in the presence of the enemy and under fire isinfluenced by factors which are absent inthedeliberate and undisturbed choice tha tcanbe made whenpreparing a rearward l ine . The two problems are quite dis tinct andcall for different methods.3 0 . Ford eliberate location a careful reconnaissance is made firsttodeterminethegenerallineofdefenseandthepointsorlocalitieshaving special importance and calling for special treatment, andtheninmoredetailtodecidetheformoftheworkstobeconstructedfor the defense of the tactical features and localities laid downinthegeneralschemeand them ethodoftreatingtheinterva lsbetweenthese strong poin ts and localities. As a re su lt of th is detailedreconnaissance, large-scale plans aremade showing the exact sitingandconstructiondetailoftheessentialworks.

Flanks.If the flanks of an intrenched position do not rest onimpassableobstacles,theym aybeturne dbyanactiveenem yunlessspecial defensive arrangements are made. The best method is to refuse the flanks gradually by trenches in echelon until somesupporting poin t is reached. The flanking trenches should not beturned obliquelytoth emain front, asthis exposesthem to enfiladeand doesno tseriouslyincreasethecircu itofaturningmovement.3 1 . Trace.Acommontendencyistomakethetrace toostraight.Anirregularlinew ithfrequent salientsand reen trantsgivesgreaterfacilities for concentration offireover any desired area and for the


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CONSTRUCTION AND EQ UIPM ENT OF TR ENC HES. 19most effective employment of machine guns. Such a trace willexposeshortlengthsoftrench toenfiladefire, b u tt he effect can bereduced by proper traverses. The enemy 's line 'will also be insalientsand reentran tsand willbeeq uallyexposed toenfilade fromourside.Minor irregularity of trace is essential and should always beobtained. The creation of large salients to include an importanttacticalp ointwilldepend upon the following imp ortant conditions:(a) Whether the possession of the point in question by us willfacilita te future offensive action without unduly weakening ourline.(b)W hether its possession by the enemy will seriously threatenthe security of our trenches.3 2 . The permissible traces for communicating and approachtrenchesaretheindentedline,easytodisputeincaseofattack,andthe zigzag, which gives bette r defilade. The litte rs evacuatingwoundedm ovemorereadilyinth e latter trace.Thebest type is the winding one, bu t the curves must be sufficientlypronounced togive real protection against enfilade fire. Iftraversesareusedincommunicatingandapproachtrenchesthebestkind is the island traverse with the trench goinground it on bothsides.33 . Concealment.Aerial reconnaissance makes concealment ofapositionimpossible,butisolatedworkBandgunemplacementscanbehidden and trenchesin woodsmay escapeobservationif clearingisnotoverdone. Airplanephotographsshowclearlyeverytrench andtraversein open country and even wireentanglements. Neverthelesseveryeffortshouldbemadetomaketheworkinconspicuous,todeceivetheobserversbydummytrenches,toavoidpathsortracksthatcallattentiontoworksotherwisewellhidden,andtoavoidtheconstruction of fresh trenchesim mediately before an attack whichwouldreveal the fact that an attack wasintended. Workdoneonbuildingsthemselvesis easilyconcealed from airobservers, b u t th eexistence oftrenchesaround or leading to a building gives a clearindicationofitsoccupation.3 4 . Buildings. Substantial buildings found close to the lineofdefensemaybedemolishedorthe ymaybeoccupied. Thedecisiondependsgenerallyontwopo ints,w hether th ey hav e cellarswhichcanbeimprovedintogoodcoverandwhetheritispossibletodemolish them. Buildings draw artilleryfireand unlessgood covercanbe constructed in connection with them th ey are nothingb ut shelltraps. Solidblocksofbuildingsw ith cellarscanbem adeintogood


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20 CONSTRUCTION AN D EQ UIPM ENT OF TR ENC HES.cover as a ru le and had be tter be occupied . A build ing withoutcellarsmayb e left outofth e lineif it canb e soeffectively demolishedastoafford nocover tothe enem y.

3 5 . Woods.Apositionfrom30to50yardsinsidetheedgeofthewoodwillafford concealmentfromobservationandaccurateartille ryfire and will deny the edgeof the wood to the enemy. The frontedgeshould under no circumstances be occupied asit furnighes anexcellentrangemark forthehostileartillery . (Differs from par.23,Par tV, E. F. M.) If awoodhastobe left unoccupied in the imm ediate front of anintrenched linespecialarrangementsmu stbe made for th e concentra tionoffireonth enearedgeofthewoodandonthegroundbetweenitand thefront trench. PROFILES. 36. A narrow trench is desirable as it presents a smaller target.There must, however, be enough width to permit the constructionofafiringbanquette and of a certain deeper space at the rear partof the t rench to allow men to pass behind the firing line . Also enoughslopemustbegiventhewallsandtheembankmentworktopreventcrumbling.Unrevetted trenches even with side slopes as flat as 1on 1aresure to cave in . A good berm 12 inches wide and reve tment aretherefore essential. Them inimum width at the bottom is 2feet6inches , or be tter 3 feet, bu t 3 feet should seldom be exceeded;greater width reduces the pro tection too much . Revetted sides

shouldhave aslopeof4on1or3on1andnotbe cutvertical. Thedepth from th e topofth e parapet tothefloorboardorbottom ofthetrenchshould ben otlessthan 7feet if possible. Heightofparapetwilldependonthesiteandthedepthoftheditchesfordrainage.3 7 . Firing trenches.Thefiguresg iven on p la te I I I are typicalsectionssuchascanbeexcavatedingoodsoilwhentimeisavailable.In actual practice they will be rougher and more irregular, with

slopesdepend ing on the consistency ofth e soiland the time at thedisposalofth e troops,b u t an effort should aiwaysbemade tofollowtheprescribed linesofexcavationasaccuratelyaspossible. Smoothand even slopesand crestsofvisible earth embankm ents and parapetsshould be avoided. Roughsod, grass,bushesor clodsof earthshouldbousedtobreakthecontinuityofstraightlinesandtomakethemmergeintothesurroundingfeatures. Itw illbenotedtha t thefilingb anq uette is 5feet below the interior crestinstead of 4^ feetasgiven in the Engineer Field Manual and Field Service Regulationswiththeideatha tthe menwhooccupythem willbuildu p the


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CONSTRUCTION AND EQUIPMENT OFTRENCHES. 21banquetteornotchorloopholetheparapetwhentheytakepositioninthem.It isbothanadvantageandastandingrulethatif donebymilitary labor, riflemen should themselves construct the trenches theyaretohold.Thebestty pe appears tobe atrench with afiringbanquette, forfive or six rifles in each bay, between two traverses each 6 feetthick,andwiththebackpartoftheexcavationformedintoacommunicating trench for observation and manningof parapets. Thistrenchissomewhatdeeper and 3feet 3inchesw ide.Anothertypeoffiringtrenchhasaminimum,widthof28inches,in order toafford the firer better protection; 1ftto 20yardsin rearthere is a second trench which permits communication and conta ins the shelters. The essentia l point in train ing i s tha t oneofthese types should be adopted as the normal type suited to the localconditions,andthetroopsshouldbethoroughlytrainedinitsconstruction.38 . Every firing trench should fulfill the following essential conditions:(a )Theparapetmustbebulletproof.(6) Every man must beable tofireover the parapet with propereffect; that is, sohe can hit the bottom of his own wire entanglement.(c)Traversesmustbeadequate.(d )A parados must be provided to give protection against thebackblastofhigh-explosiveshell.

(e)The trace ofthe trench should be irregular to provideflankingfire.( / ) Andif the trench is to be held for any length of time, the sidesmustberevettedand thebottom ofthetrench mustbe flooredanddrained.Thenarrower the trenchthe better the cover, bu t if toonarrowi t may hamper the movement of troops too much. Therefore, a firingtrench is usually made broad enough to allow of movementbehindthe l ineofmen manningthe parapet. Every manm ustbeabletousehisrifle overthe parapet, and the menm ovingbehindmustnothavetostoopdownlow in order to gettheir headsundercover.Theresultingsectionis,therefore, with ab anquette orfiringstep18incheswideand 4feet 6inches(or5feetif weallow fora smallnotch or hollow to hold the rifle) below the crest of the parapet,and behind this a deeper portion from 18to 30inches wide at the


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23 CONSTRUCTION AND EQUIPMENT OF TRENCHES.bottom, and from 6to 7feet below the crest l ine of the parapet.The firing step must have a level surface to give a firm foothold.I t mayconsistof an earth step revetted withplankaheldin placebystakes.Quotations from Solano's Field Entrenchments, page 43: "T herifleman must not expect toobtain bullet-proof cover ofan y valueatcloserangeinlessthan35to45minutes'workathastyintrenchingunder fire. The mere fact, however, ofobtaining concealmentfortheheadandshouldersisofsomemoralvalue,eventhoughthemound of earth forms for a time a better target to aim at than didthebodyalone. Bxitoncethe rifleman hasobtainedgoodfirecoverthevalueofhisfire,thechancesofhissurvivaltousethebayonet,and the difficulties of driving him back by fear or panic increasesogreatly th at hiseven tual successin attack is almost a certainty,provided he does not cease to press forward to the a ttack withcourage and determination, remembering that his spade is only ameansto enable him to usehis bayonet as quickly and effectivelyaspossible."

3 9 . Communicating andapproach trenches.-Lessemphasisislaidonthefiringtrenchesthanonthecommunicatingtrenches,becauseincaseofnecessityresistancecanbemadeinanykindofatrench,whilein a communicating trench out ofrepair orbadly madeit isimpossib le to move freely and promptly . This does not justifyinferior firing trenches when time permits of good work. Theyshould be of clear-cut design and well made and kept in the bestrepairpossible. (PI . I I I . )Ty pes arenowbecomingfixed and in France the following seemtobeth enormal: Comm unicatingandapproachtrencheswelltotherearare6feetwide,thosefartherforward3feetwide,andbothtypes6feet deep. Acommunicating trench less than 3feet wideat thebo ttom is sure to become b locked . This is the minimum to beallowed, and the work should be commenced with a width of notlesstha n 3feet 8inches at theto p, soastoget.3feet at the bottomaccording to the stiffness of the soil. Trenches for l ight railwaysmaybeasmuchas10feetdeepand8feetwide.Bermsof1footoneachsideofasaportrenchwhereearthispiledu p are considered indispensable . They prevent s liding of ear th ,and furnish a little shelf on which to place tools, bags, guns, andotherarticles,in casetroopswanttopasstheoccupan ts; the doublebermalsomakesitpossibleforinfantrytoleapoutofatrenchwhentheemergencyrequires.


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CONSTRUCTION ANDEQUIPMENT OFTRENCHES. 234 0 . Earthworks built entirely or largely above ground are used

only when wet, ill drained, or rocky ground compels. They affordgood cover and if the parapets are about10feet thick at the top, withgentle front slope, and have had time to consolidate and dry out,they are said not to suffer much more from heavy artillery bombardment than do the usual types of trenches with low parapets.

They are, however, very conspicuous, especially when new, andrequire great time and labor to build. They are much more comfortable for the troops sheltered behind them. The ditch excavationin front may be used as an obstacle and filled with wire. Thereshould be at least a 2-foot berm at the foot of the exterior slope sothat this is not likely to fall into the ditch. Parapets of sandbagsexclusively are much more vulnerable than those of earth, and areof expensive material; they should be avoided except for minorworks, such as blocking a trench toward the enemy, barricading aroad and the like. They may be used in emergency in the firstzone if haste or silence is paramount importance.

TRAVERSES.4 1 . Traverses are solid masses of earth extending from the front

wall of the firing trench or sometimes from the rear wall dividing thetrench into a series of compartments whose purpose is to decreasethe exposure of the men to enfilade fire and to localize the effect ofa shell bursting in the trench. Traverses must be strong and solidand when possible should consist of the undisturbed earth. Theyshould be from 2 to 4 yards thick and should overlap the width ofthe trench by at least 1 yard, and should be well revetted. Theclear distance between traverses is that necessary to accommodatea small number of rifles, say those of a squad of 5 to 8 men; the distance therefore is from 5 to 8 yards. (PI.III.

Traverses in a trench facilitate bombing attacks along its lengthby an enemy who may have entered it as grenades can be thrownfrom under cover of a traverse into the second compartment beyond.A longer compartment to prevent this may be occasionally placedin the line of the trench. This long bay should be straight, and thetraverses on either end should be loopholed for fire into it. Bombingtrenches or pits behind the front line are also useful to stop this formof attack.

Where traverses have to be built in a completed trench insufficiently traversed, they must be made in embankment using theearth excavated to form the passage round the traverse and supplementing it with sandbags or other revetting material.


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24 CONSTRUCTION AND EQUIPMENT OF TRENCHES.4 2 . For approach trenches thebest typeis the island traversewith the t rench goinground i t onboth s ides. Sections of t renchsubject to special exposure are sometimes protected with "bridg e

traverses,"builtacrossthetopofthetrenchonsupportsoftimberors teel. (PI. I I I . ) HEAD COVER.4 3 . Head coveristhetermappliedtoanyhorizontalcoverwhichmaybeprovided abovethe planeof fire. I t isobtained by notchingorloopholingthetopoftheparapet.Notches.When the relief of the trench is toogreat for a manto

firestanding, orwhentheheightoftheparapet is more than 1footabovetheleveloftheground,notchesshouldbemadeintheparapet.Thesimplestw aytomaketheseand givesupporttotheir sidesandmake them the least visible is to arrange sand bags on top of theparapet.Loopholes.Whenoverheadcoveri&used,loopholesarenecessary.Theym aybecollectiveorindividual (PL I I I ) ,constructed ofsandbags,wood, steel, hurdles, orother material. They should beconcealed by usinggrass,brush, canvas, orempty sandbags. Theskyasabackgroundshouldbeavoidedbyraisingtheparadosorplacingacanvascurtainbehindthem,andclosingtheopeningwithametalcoverw hich can be removed when the loophole isin use.In addition to their visibility, loopholes have the disadvantagetha tthe y causeapauseinthefireofthedefender wben the attackreaches the most deadly zones of fire, because the defenders havetowithdraw theirrifles toprepareforbayonet fighting. I tistherefore necessary to arrange for fire over the parapet. For this purposebanqu et te scanbeconstructedofsod,stones,logs,orscaffoldingbetween the loopholes. In a ll firing trenches, however, a fewloopholesaredesirablefortheuseofsnipers,andtheremaybeoneortwobetw een eachtwotraverses. Allnig htfiringisovertheparapet.

In some sectorsthe loopholesshouldhav e the ir axes inclined tothe normal to secure flankiDgf ire. Every loophole intended forobservationshouldbeplacedobliquelyintheparapetinordertobeprotected against shotsfrom the front. The bottom of a loopholemust bein the plane offirethat sweepsthe ground in front.

OVERHEAD COVER.4 4 . The defenders of a t rench must have shelter against bom

bardment by high-explosive shells and against the weather.This is secured by traverse, narrow trenches, and shelters. (PI.I I I . ) Sheltersareclassified assplinterproofsofbombproofs accord


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CONSTRUCTION AND EQ UIPM ENT OF TRENCH ES. 25ing aa they are designed to afford protection against the splintersofshellsburstoverornearthemoragainstshellshittingthemdirectandburstingonimpact. Distinctionbetweenthetwoisimportant.4 5 . Sheltersinthefrontwallofthefiringtren chund ertheparapetmade by undercuttingareobjectionable. Eve nif carefully shoredupthe yweakentheresistancetotheb urstofahigh-explosiveshell.A certain amount of splinter-proof covershould beprovided in thefront line, and it will also serve asprotection against th e weather.The bestplaceforitisin thewallsofthecovertrench. It mayalsobeplacedbehindtheparados.46 . Bombproof shelters safe against heavy high-explosive shellhave to be dugvery deep and entered by a narrow opening and steps. This meansdelay for the men in gett ing out of the bombproof,andeverymomentisimportantinawell-plannedattack,astheenemyw illmakeasudden assaultalmostatthe mom entthe artilleryliftsitsrange. Deepcoversheltersarethereforeinadmissibleinthefrontline exceptforth eprotectionofmachineguns(forw hichspecialliftsmaybeprovided)andtheirdetachmentsandforcompany command posts. They are also dangerous in an a ttack bygas. They are generally confined to the position of the battal ionreservesand to the strong pointsth at may form ap art of the frontsystem. They may be used elsewhere, however, if the soil and natural features are favorable to their construct ion and arrangementscanbe made togetth e men out ofthem quickly.Theentrancesmust be covered tokeepoutsplinters. They are,therefore, masked either by a turn in the approach trench orby atraverse or splinter proof of gabions or eand bags. Each sheltershouldbeprovidedwithtwoentrances,ofwhichonemayconsistofasimpleex it without head cover, with alittle stairway tobe usedin case the main entrance is obstructed.Theshelterswhicharegenerallylargeenoughfor25menatmostshould be constructed so tha t they will conta in the men not on guard, half ofthem seated and half of them lying down.

Theroofmaybebuiltasfollows:Firstalayerofpoles6to8inchesthick, then alayer of earth 8to 12inches thick, asecond layerofpoles at r ight angles to the first, then a second layer of earth 12inchesthick.Th e water-tightnessof the roof issecured by sheetsof corrugatedirononthe top layer ofpolesorby tar paper placedonth e surfaceoftheearth,inwhichcaseth egroundshouldbewelltam ped . I tiswellto place brush or straw between the aheetiron and th e earthabove,alsotoplacebranchesonthefirstlayerofpoles.


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26 CONSTRUCTION AND EQUIPMENT OF TRENCHES.The railsor beamsm ust have agood margin of strength beyondtha t necessary to support the load above them, soas to stand theshock of the explosion. I t will be seen tha t this roof is fully 6

feet th ick . Hence, the shelter will require to be a t least 10 feetdeepifitspositionisnottobetooconspicuous.Fortype sofshelterswithb illsofmaterial, seePlateV.Followingisadescription otatype ofdugout construction.Dugouts.The construction of the dugouts has been carefully studied and designed tow ithstand shell fire. Thereisfirstalowerroofm adeofcurved corrugatedironcoverwithtwoorthree layersofsandbags, and above iliisisan air spaceof not lessthan 18inches,over which is placed steel 6-inch I beams; then another air spaceandlayerofcurved corrugatediron,upon which aresandbags,steel6-inch I beams and earth , and on top of a ll a detonating surfacemade of broken brick or stone, the idea being to have the shells detonate ontop of upper roof at the surface of the ground and notpenet rate through airspaceinto lowerroof before exploding.47 . Th e extended useand effectiveness ofartillery fire demandsanincreasein th enum ber and strength ofsheltersprovided for themen. The lightsplinter-proofs arereplacedby shelterswithstrong-roofs. Th isispossiblebecause the great depch of the trenches furnishesearthforathickerroofwhichisfurtherstrengthenedbylayersofresistingmaterialssuchassteelrailsorbeams,timbers,plateiron,concrete,orbrick.The shelters under the parapet are frequently dividedinto twostoriesbyanintermediate floororplatformleavingineachstoryonlysufficient head room to accom modate m en lying down. Thisa rrangement enables a larger number to be p laced in rela tively strongershelters.Underground or cave shelters (PI. I l l ) have become deeper andnowaremadewith25to35feetofsolidearthascoverwithneverlessthantwoentranceswhicharecurvedorbrokentokeepoutsplinters.Communicating trenches and approachesbetween firing and covertrenchesaregenerallyblindedthroughouttheirwholelength.48 . " S l i t " trenches, orverynarrowtrenches1or2feetwideand7feetdeep duga tright anglestoapproach trenches, form goodprotection against hostile bombardment. They must be braced nearth etoptoprev en tcavingin . Theyshouldbelongenoughfor10or12men. Controlofthe menismoreeasytha nin th ecaveshelters.4 9 . General principles. Everydeep cave shelter must have twoor more separate exits to facilitate rapid egress and to prevent ablockadebythedestructionofoneexit.


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CONSTRUCTION AND EQUIPM ENT OF TRENCH ES. 27Roof timbers must always have three orfour times the streng thnecessarytosupportmerelytheloadduetothethicknessoftheroof.Thisallowsfortheshockoftheshellaswellasforthecontingencyth at anewgarrison maypile2or3feet moreofearth ontopof th e

existingroof.Arectangular timber willsupport moreweight if seton its edgethanifsetflat.Theendsoftimbershouldneverbesupportedonsandbagwallsorevendirectonsolidground. Astrongtimberframeshouldalwaysbeusedontwooppositesidesof th e shelterto supportt he endsof rooftimbers.A"burster"layerof6inchesto12inchesofbrickorstoneshouldalways be provided near the top surface of the roof. Over thisbursterlayer should be a layer ofn ot lesstha n 6inchesof earth todecreasedangerfrom th escatteringofthestoneorbrickb ytheburstof the shell. As the object of the burster layer is to explode theshell near the surface, i t will be to a large extent defeated if thelayerofearthaboveit ismademoretha n12inches thick .Cavesheltersmustbeventilatedandtheventilatormaybeutilizedforaperiscope.Splinter-proofcoverisafforded byalayerof logsorbeams6inchesormorein dep th coveredoverwith notlessthan 12inchesof earth .(Differs from par.14,Par tV,E.F .M.) The following forms aroofproof againsta 6-inchhigh-explosive shell: Alayerofrailsorbeams,18inchesof earth, a layer of brick, 2\ feet of earth, another layerofbrick6to12inchesthick,andoverall6inchesofearth.

REVETMENTS.5 0 . Thedeepfiring,cover,support, reserve, comm unicating, andapproachtrenchesnowconsiderednecessaryrequirecarefulconsideration of suitable revetments, especially where the soil does notweatherwell. Tokeepth emencomfortable andthetrenchescleananddryrequiressomethingmoresubstantialthantheusualtempo

rary revetment, such as brush, sod,and sandbags. Some soils areapparen tlyfirmandstandatasteepslopewhenfirstexcavated , b u tunder the action oft he weather the sidewallssoonslough off, obs truc t the trenches, and make them muddy in rainy weather. In case of long continued occupancy of the trenches, revetments oftimberandplankwillgraduallyreplacethelighterforms,andboardsandgratingswillbeusedtofloorthebottomofthetrenches.Inregionsnearcementmillsandwheregravel,sand,ruinedwallsandhouses,orothersuitablematerialscanbefound, concrete blocks


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28 CONSTRUCTION AND EOTIPMENT OF TRENCHES.or concrete molded in place may be used for revetments and forflooring th etrenches.Aconvenientsizeofridewallblocksis10by8inchesby6inchesthick,andforfloorblocks30by20inchesby4inches th ick . S idewallblocksshouldhavetwoprojectingwireloopstoserveashandlesin carryingth e blocksthrought he trenchesand in anchoring themin p lace . These blocks afford a nea t and substantia l r evetmen twhich contributes materially to cleanliness. They are also usefulforbuildingsmallcoveredobservationstationsalongtheparapets.51. Someoftheformsoftemporaryrevetmentsare:Sandbag.

Brushwoodhurdle.Wire-nettinghurdle.Continuoushurdlework.Expandedmetal.Rabbitwire.5 2 . Sandbagsare la id as headers; i . e ., the length of the bagatright angles to the face ofth e revetment or asstretchers; i. e., thelength of the bag in the plane of the face of the revetment . Therevetmentshouldslopeatanangleof4to1,andthereforethegroundonwhichthebottomlayerorcourseislaidshouldbeataelopeof1to4. Thesandbagesmustbebonded,i.e.,th ebagsofeachcoursemustbreakjointw ith the bagsofthe coursesabove and below. Acertain number of headers must be used to t ie the revetment intothebank. I tisusualtolaysandbags withoneheaderto everytwostretchers.Whenfillingsandbagsthebottomcornersmustbewelltuckedinandithelpsifthemouthofthebagisturnedoverforabout 3inches.Th ebagthen staysopenmoreeasily. Bagsshouldbe three-fourthsfilledand caremustbetakentoob tainuniformity inth is,forunlessthebagsareallthesamesizetheywillnotbuildupreadily. Asandbagwhenfilledshouldmeasure20by10by5inches.Th elineofrevetment mustbe prepared by digginga notch withth e bottom at aslopeof1to4and broad enoughtotak e aheader.Sincetheheaderis20incheslongthebackofthenotchshouldbe5 inches below the front. If the face of the revetment is kept a trightanglestothebottomofthisnotchtherequiredslopeof4to1willbeobtained.I n laying the bagsth e mouths of the bagshould be folded overunderneatht he bags. T he mouthsoftheheadersand th eseamsofthestretchersshouldbeturnedintowardthebacksothatifthebagbecomes untied or the seams burst the earth will not fall into the


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CONSTRUCTION AND EQUIPM ENT OF TRENCH ES. 29trench. The bagsshould be beaten, withaspade, maul, or shovelintoarectangularshape,otherwisethebagsdonotgetafirmseating.Thefaceoftherevetmentshouldbequitesmoothandnotlumpy.Unlessitiscertainthattherevetmentisnottobeextended,theendsshould be leftirregularsotha tan y extensionw illbebonded to theexisting revetment. I t is best to finish off the parapet of afiringtrenchwitharowofheaders.53 . Brushwood hurdles a re usually made 6 feet long and of therequired height. The pickets should project 18inches below thebrushwood and be sharpened for driv ing into the ground. Theyshouldbeabout3inchesindiameterandshouldbespacedapproximately2feet apart; that is, four pickets toahurdle. Actually thetwo outer pickets should be about 6 inches from the ends of the hurdle. T he pickets are therefore 1 foot 8 inches a part. T hebrushwood should be 1 inch to l inches in diameter and of ash,willow,orotherpliablewood.Toconstructthehurd le,driveth e picketsintothe groundfirmly,and 18inches from the bottom of the pickets run two strandsofp la in wire along the p icke ts, tak ing a turn round each p icke t.Twist these wires together until they are quite t ight, then weavethe brushwood in and out of the pickets, beginninga t the bottomand keeping i t pressed firmly down on the wire . Each lengthofbrushwoodshouldpassalternatelyinfrontofandbehindthepicketsandif apiece,ofbrushwoodisbehind the picket the piecene xt ontop should be in front of i t , and so on. If the brushwood is notlongenough toreachthelengthofthehu rdle ,twistanotherpiecetoitortieapiecetoitw ithwire. I tisseldompossibletobendapieceof brushwood round the end p icke t and take i t back along thehurd le , so le t i t p roject about 6 inches and cut i t off. Continueuntilhalfwayup,thenputinacoupleofstrandsofwiretwistedasbefore. Completethehurdle andfinishin thesamewaywithw irealongthetop. Thensewthehurdleinthreeorfourplacesfrom toptobottomwithplain wire. Thisconstructiondiffers from tha tmentionedinparagraphs30and31,Part V,E. F. M.In placing the hurdle , the bank should be cut away to a slopea l it tle flatter than 4 to 1. The hurdle should be laid against thebank and the pickets driven into the ground 18inches. The topof each picket should be anchored back by 6to 8strands of plainwire to a s tout anchor picket driven firmly at a good s lant. Theanchorpicketshouldbe about 3feet longand driveni n 2feet. Itshould never be lessthan 10feet from the levetm ent even in goodground,andmaybeasmuchas30feetawayinbadholdingground.


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30 CONSTRUCTION AND EQUIPMENT OF TRENCHES.If the holding power of the ground is good all four pickets of ahurdle may be anchored back to oneanchor picket . If very bad,each picket may requireitsownanchor. The anchor wiresshouldbe windlassed up tigh t. The anchor wires should be fastened to the anchor picket at ground level and toth e hurdle just above thebrushwood.54.Rabbit-wire hurdles.Thefollowingisperhapsthebestwayofusingrabbitwireorpoultrynetting:Three pickets, each6feet longand of3by 2inch timber are laidon the ground paralle l to each other and spaced 3feet apart. A5by 1inchplankisnailed toallthree 6inchesfrom oneend. An

otherplankisnailedtoallthree18inchesfromtheotherendandathird plank dividingthegapbetweenthe other two. Diagonalsarethen added from the top of each outer picket to the bottom of themiddlep icket. Each diagonalisoftwostrandsofplain wirewindlassedu ptight. Therabbitwireislaidontopofall,stretched tightand fastened to p lanks and p icke ts with nails and staples. Theends of th e pickets projecting 18inches are sharpened for driving.The anchor wiresare pu t on the picketsclosetoth e topplank andanother 5-inch plank is then nailed on flush with the tops of the pickets.

5 5 . Continuous hurdle work.In this case the bank is cut backto a slope of 4 to 1, stout 8-foot pickets are driven in every 2 feet6inchesor3feet,withtheirfeet4 to 6inchesfromthebankanddrivenin 18inches. Thesepicketsshould be driven at a slopeof 4to1.Th ebrushwoodisthenwoveninandou tofthepickets. Thebrushwood is bent around the corners. The pickets are anchored backin the usual way. Therevetment is f inishedoff with twoor threestrandsofplainwiretwistedtogethertightlytopreventthebrushwoodfromcomingoffthetopofthepickets.5 6 . Expanded metalismadeoutofthinsheetsofmetalslitandthenpulled out to form a mesh. The sheets are usually 6 by 3 feet.They are quite light and one man can carry th ree sheets. Thismateria l makesa good revetment. I t is best to carry i t up to thetrenchesalreadymadeupintopanels.Puttwosheetsofmetaledgetoedgeandoverlappingtosuchanexte nt tha tth e sheetstogether makeu pth erequisite height oftherevetment. Theoverlapshouldnotbelessthan6inches. Sewthetwosheetstogetherstronglywithplainwire. Takethreelightpoles1to2inchesindiameterandlaythemonthemetalparalleltothe

longedgeofthe sheets, onenearthe top, onenearthe bottom, andonein the middle. Sewthese poles to the metal with plain wire,


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CONSTRUCTION AND EQUIPMENT OF TRENCHES. 31s tarting and finishing 9 inches from the edge of the metal , thusleavingalengthof9inchesateachendofeachpolenotattachedtothe meta l. The panel can then be rolled up and carried in to thetrench.To construct the revetment, cut the bank back to a slope of 4 to 1. Lay the panel against the bank, the poles horizontal, thepanels overlapping; that is , the edge of the metal of one panel isslipped in between the poles and metal of the next panel. Thepoleswillthenoverlap9inchesandthemetalwilloverlap9inchesbeh ind them. Take good 8-foot pickets 4 inchesin diameter anddrivethemonaslopeof4to1tightagainstthepanels,oneateachoverlap and onebetween the overlaps. Anchor backi n the usualway.In getting round traverses the horizontal poles must be omittedand the panels cut vertically from the top about three-fourths ofthe waydown. One-halfisthen allowedtoslidebehind the other,thuskeepingtheslopeof4to1.57. Continuous rabbit-wire revetment.Useslightlylighterpickets2$to3inchesindiameter. Cut thebankbackto4to1. At intervalsof2feet or2feet 6inches, cu tv erticalgroovesin th e ban k bigenoughtotakeapicket. Driveapicketwithitsfootinthe bottomof each groove. Donot drive in more than 6 inches and le t thepicketstandafewinchesclearofthebank.Then at the bottom, half way up and about 6inches below thetop ofeach picket, run two orthree strands of plain wire, twisteduptaut . Thebottomstrandsshouldbepu tonfirst,thenthem iddle,then the top, soastoavoid loosening the wiresalready pu t on byovertwistingthenextones. The nru ndiagonalsofsimilarlytwistedwire from the top of each picket to the bottoms of th e pickets onboth sides. Whereth e diagonalsand horizontal wires crossin themiddleofthepanels,jointhemtogetherwithashortpieceofplainwire. Thisgivesaframework toholdtherabb itwire.Run therabbit wire behind the framework; tha tis,between theframework and the bank. Pull i t as t ight aspossibleand attach it to theframework in many placeswith short lengthsof plain wire.Put onthe anchor wiresand draw the poles up against the bank.Then drive the poles tight home. Tighten up the anchor wiressoas to draw the poles into the grooves. The rabb it wire is thenbroughttightagainstthebank.Angleironsmaybeusedforanchor pickets. Anchorp ickets andwiresshouldbeburied.


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32 CONSTRUCTION AND EQUIPMENT OF TRENCHESDRAINAGE.

58. Drainage is essential to the preservation of the trenches andthehealth and comfort ofthetroops. In deliberate worksitiswelltostudy the drainage questionin detail and to dig special ditchesofamplecapacitybefore workonthetrenchesproperisbegun. Ofcoursethis cannotbe donein the presence of the enemy. Abouttheonlyremedyinthatcaseisthecollectionofwaterintopita,theuseof constant pum ping, and th e constructionof floorsorgratings.Thebottomof the trenchshouldslopetoward the back, wherethewatermayberu ntoapi tinadrain. Wherethesoilisimperm eableanendeavor should be madeto reach a permeable layer by boringwithanearthauger. In hillyterrainth ew aterm aybe drainedoffbypipesplacedunder theparapet. (PLII I .) If a permeablelayercannotbereached,thedrainagepitsmustbeemptiedwithbucketsorpumps.59 . The drainage and flooring of approach and communicatingtrenches constan tlyused isspeciallyimportan t, and shouldbeconsideredinth eirlocation. Whentimberforflooringisnotavailable,drainsfilledwithbrokenstoneshouldbeconstructedinthebottomof th e trenc h. A good form offloorgratingis in lengths of6 feet,18to 24inches wide, made of crosspieces of % by 4inch boardsnailed totwolongitudinal piecesoftimber about 3by 4inchessetonedge.6 0 . Insheltersprovision skouldb emadeforthe drainageofwaterwhich runs through the entrance or seeps through the walls. Adrainagepi t should be constructed near the entrance and the floorofth e shelter should beelopedtoward it; the pit must beemptiedwhen necessary. (PI. I I I . ) Theroofs of sheltersshould bemadewaterproof byusingroofingpaper, corrugated iron,tin orzinc,linoleum,canvasortiles. LATRINES.

6 1 . Latrineaccommodationshouldbeample;seatsshouldbebasedona t least 2per cent ofthe troops usingthem . Urinereceptaclesshould be based ont he same scald. The best location for latrinesandurinalsforthefiringlineisbehindthecovertrenchinT-headsattheendofshortbranchesleadingofffromit . (PLII I .) Latrinesshould be provided fora ll trenches and shelters which have tobeoccupiedevenforshortperiodsbytroops.6 2 . The following aresomeofthevariouskin ds :(a) Deeptrenchwithboxontopor"box latr ine ."(6) Buck ets.(c) Shorttrench system.


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CONSTRUCTION A ND EQ UIPM ENT OF TRENCH ES. 33Boxlatrine.This consistsofa pi t 15feet longby 2 feet wide by6feet deep. Asquare boxorboxes are placed on top. The s idesshouldbeboardedallroundsothattheboardsprojectoverthesidesof the pit . Theheight of the boxshould be17inches. Twoholesaremadeinitandalidprovided. Ifdeepenoughitdoes notsmell.I t ismostsuitablefor trenches, provided the ground is dry. Boxlatrinesarenot suitable forpositionstha t aretobe occupied a longtime.If therearefrequent approach trenches, sayoneevery 100yards,a goodposition is just off the approach trench. This may not besuitable,depending on the trench; in some casesasuitable site is

atthecornerofatraverse.Bucket system.Ifthegroundiswetanddeeptrenchescannotbedug, the bucket system is most suitable for trenches. Any metalreceptaclewillactasabucket. The excretamustbe covered withearth. I t is very important tha t every officer, noncommissionedofficer, andmanshallmakei tahabittocoverth eexcre taevery tim ebeforeheleavesth elatrines. Officers andmenareap ttoforget thisandinfiveminutesexcretawillbecoveredw ith flies. Th eb ucke tsare removed and emptied a t night. They shouldbe emptied into a deep p it somewhat in rear of t he su ppo rt tren ches. This p itshould be covered, screenedfromflies,and burned out at intervals.Theshorttrenchsystemissuitableonlyonthelineofmarchwhenahaltismadeforanight ortwo. Theseshould bedug 3feet longby 2feet wideby 1foot deepw ith4feet 6inchesinterval betweenlatrines,sothat whenth efirstlotarefull and coveredin, fresh onescanbedugbetween,leavingamarginof9inchesoneachsideoftheholeofsolidandnotfoulground.Every latrine should have a separate pi t dug for a ur inal. Thefollowingarethevariouskinds:(1) Pit with tin can on top. Thepurpose will beserved by anypit 3feet deep and 3feet in diameter, with stonesin the bottom,covered overwith atin can perforated atits bottom placed on thestones.(2) Trough system.Thisis more e labora te and suitable for apermanent camp. Atroughslightlyinclined, 2feet long, madeofwoodlinedwithzinc. Oilcanatoneendoutonth eground, placedtocatchflowfromthetrough.(3) Pipesystem.This consists simply of an oil can,w ith apipesoldered on,conductingth eflowtoapit 3feet deep. Thisis cleanandsimple.

89454 17 3


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3 4 CONSTRUCTION AND EQUIPM ENT OF TR ENC HES.(4) In trenches i t is sometimes impossible to dig a pi t and anordinary oil can placed in asuitable position as container can beused.Disinfectants.Bleachingpowder (chloride of lime) should befreely usedateverylatrineandurinal. Allgroundwhichhasbeenused forlatrinesshould alwaysbemarked "foul gro un d."

OBSTACLES.63 . Tactical use.Theuse of an obstacle is to check a hostilerush and delay the enemy under the closefire of the defense. Anobstacleshould be at suchdistancefrom th ep arapet th at it is difficultforhostilebomberstocrawluptoitandthenthrowbombsintothetrench . Onth eotherhandth eobstacleshouldbeundercloseobservation and under closefireofthe defense. If the front edgeof thewireis 40yardsfrom the trenc h these conditions are fulfilled.6 4 . Concealment.Thevalueofanobstaclewillbeincreasedanditsliability toinjury by fire decreased if th e obstacle is concealed.Ifitispossibletoplacetheobstacleinafoldinthegroundsomuch

thebe tter. I tissometimespossibletoplacetheobstacleinabroadshallowditch. In tha t caseth edeepestpartofthe ditch shouldbetowardtheenemy. Theearthshouldbecarried backandplacedintheparapet.6 5 . Construction.-The obstacles should be made in such awayth at th e following conditionsare fulfilled:(1) The working party constructing i t should be extended andnever bunched together.(2) Silence must be preserved. Therefore everyone must knowexactlywhathehastodo.(3) Speed isnecessary. Theworkm ust therefore be methodical,each man having aspecific task.(4) The working party must never have an obstacle between itandthetrench.(5) The obstacle should be one that can be improved and thickened up easilyand quickly.(6) The obstacle should be of a type that will suffer as l it tle aspossible from hostile gun and small arm fire and from rifle andmachine-gun fireofth e defense.Thefollowingpagesshowhowobstaclescanbeconstructedtofulfillasmanyoftheseconditionsaspossible:6 6 . Lowwire.Thepartyshouldconsistof32workers,ifpossible,exclusiveofnoncommissioned officers. Formthep artyintworanksandnum ber theminthreesboth front and rearrank. Theleftf ile


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CONSTRUCTION AND EQUIPMENT OF TRENCHES. 35isnot numbered. For the sakeof explanation, letters are given tothesepartiesofthreeasfollows:

oB 0 cKHFD0 oA 0 oIoGoEoc

Assumethattwobaysoflowwirearetobebuilt.Descriptionofobstacles.Theobstacleconsistsof3foot6 inchpicketsdriven about 1footintothe ground. Atthe end ofeachrowofpicketsisashortanchor picket slopingback awayfrom th e lineoftheentanglement and about3feetfromth e endpickets. Therowsare 3 yards apar t and the p icke ts ineach row are 3 yards apart .Thepicketsareplacedinquin cunxorder;tha tis,thoseofthemiddlerowdividethegapsbetweenthoseofth eouterrows. Atau t strandofbarbedwireisrunalongeachrowatkneeheight,beingmadefastwith a round turn to each p icke t. Between the midd le row andeach ofthe outer rowsisa diagonalw ire, tau t and at knee height,running from the first outer row picket to the second center rowpicket,thesecondouterrowpicketandsoon.Restingonth ediagonal and halfway betweenth erowsofpic ketsarelaidtwowires,oneoneachsideofthecenterrow,quiteloosesoth atthe yloopaboutontheground. Theseloosewiresare fastenedtothediagonalsbytwistingthelooseanddiagonalwirestogetherineveryotherplacethattheycross.Duties ofparties.Parties Aand Bgoout almost simultaneously.Party Adrives the first rowofpickets, and soneeds am aul. Themaulmanshouldbetall. Onemanmauls,onesuppliesthepickets^onepacesthethree yardsand holdsthe picketsfordriving. KeepingcloseupsoasnottolosethepicketscomespartyBwithacoilofbarbedwire,apairofwirecutters,andtwopairsofhedginggloves.Allwirepartiescarrysimilarequipment.Starting at the anchor picket, party B runs out the first straightwire, onemanholdingand uncoilingth e wire,th eother twotakin groundturns,eachtakingtheturnsonalternatepickets.About6yardsbehind isp arty 0,apicket party which drives thesecond row of pickets , one man again mauling, one holding andpacing, one supplying pickets. This party measures the positionof each picket from the front row by going to each picket in thefrontrow,pacing 1%yardsalongtheline,turningatrightanglesandpacing 3 yards and th en plan tin g th e p ick et. This elim inatescumulativeerrors.


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36 CONSTRUCTION AND EQUIPM ENT OF TRENCHES.Starting6yardsbehindCcomespartyD,whichworksonthesameBystemasBandputsonthediagonal,keepingbehinditsownwire.Caremustbetakentomakerealroundturns.PartyErunsoutthefirstloosewire,startingabout 12yardsbehind

T>. Oneman holds the coiland unwinds i t . Oneman places thewireinpositiononth ediagonal. Thethird manclipsth eloosewireto the diagonal.PartyFcomes15yardsbehindEandrunsoutthesecondstraightwire. Party Gdrivesth e third rowofpickets, measuringthe posit ion ofeach from those of the second row. Party H starts 6yardsbehind Gand putsonthesecond diagonal. Party I starts 12yardsbehind H and runsth esecond loosewire. Party K starts 15yardsbehind I and completesthe bay withthe third straight wire.Thedirectioniskeptbythemenoftheleftfilewhoprovidethemselveswithapieceofstringortape,equalinlengthtothedistancefrom the parapet to the front edge of the wire . They goout with party A. Onem an places himself a t the foot of the parapet with one end of the s tring in h is hand. The o ther runs the s tring outunt il i t is tau t. The man on the parape t keeps the string alwaysperpendicular to the general line of the parapet. The o ther mankeeps i t tau t and moves along wi th party A. Work can be donewith parties oftwo men, bu t if oneis hi t the workis disorganized.If there are fewer parties the same party may have to dotwoormore parts of the work. Thus if there are only s ix parties AwillalsodoG'swork, B will doH 's, CwilldoI 's , DwilldoK 's. Thepicketsmustbedriven in farenoughinthefirst instance. If theyhave to be driven after the wire is on, the wire will be too low.Maulsshould be muffled with sandbagsnailed on.

Advantages of this form of obstacle.Easily thickened; quick to build; easy to conceal; not easily destroyed by hostile fire or byfriendly fire which willpassoveri t;th emen arealwaysbehind thewire ; easy to mend. This entanglement requires one p icke t and 11yardsofbarbedwireforeachyardoffront.6 7 . Th ehighw ireentang lemen tissimilarinageneralwaytothelowentanglement, bu tis4to6feet inheight. It usuallyconsistsofthree tofiverowsofstakes connected by barbed wire. In additiontothehorizontalwiresconnectingthetopsofthestakesithasdiagonal wiresrun ning from the tcp of eachstake tothe bottoms ofalladjacent stakes. Thesidetoward theenemy should be completedas an ordinary wirefence. Slight irregularities in height ofstakesandarrangementofwiresaddtothevalueoftheobstacle.6 8 . French wire.Thisconsistsofacontinuousspiralofplainwire3feet 6inchesin diameter, each turn ofwire being clipped to the


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CONSTRUCTION AN D EQ UIPM ENT OF TR EN CH ES. 37turns on both sides in five places. When closed up it looks very-muchlikeacpilofplainwire,butwhenpulledoutitmakesacylinde rofwiremesh. Ea chsmallcoilpullsouttoalengthof20yards.Abigcoilconsistsoffivesmallcoils.Advantages anddisadvantages.Itcanbeeasilycrusheddownbythrowing a weight on the top and must therefore be supported b ypickets and barbed ware. I t is easily carried and quickly pu t up .I t isheld in place by iron s taples 5 inches long. The numberofmenrequired forapartyis26. Twomenkeepthedirectionw ith astringasfor lowwire and the remaining 24are dividedinto partiesof3asforlowwire.Descriptionofobstacle.-TheobstacleconsistsoftworowsofFrenchwire. Each smallcoilisstapled downinfiveplaces,tha tisateachend,one-fourth, one-half,andthree-fourthsofthewayalong. W heretwocoilsmeetthesamestaplefastensdownbothcoils.Pickets 5feet long are driven into the center of the coilsin fiveplacesasforthe staples. Thesepicketsshouldbedrivenin at leasta foot. Astrand ofbarbed wireisrun alongth e topofeachrowofFrench wire, These strands of barbed wire a re pulled as tau t aspossible and are twisted on the French wire with astaple, peg, orpairofwirecutters ,closetoeachpic ke tand inseveralplacesbetweenthepickets. ThisbarbedwiresupportstheF renchw ire.ThetworowsofFrenchwirearetiedtogetherbyadiagonalstrandofbarbedwirerunningfromthetopsofthepicketsofonerowtothetopsofthepicketsoftheotherrow.

In addition astrand of barbed wireisru n along the front of th efrontrowofFrenchwireandtwistedtoit. Thisispartlytohold u ppeopletrying tocrawl through and partly tohold th e French wiretogether, should i t come loose from i ts fastenings. This wire ie usuallycalledthe"apronwire."After this more apron wire can be added or loose wires may binserted between the tworows. The tworowsof French wire arejustfarenoughapartforamantopassbetweenthem.Duties ofwiringparty.PartyA,firstFrenchwiringparty.A1holdsendofwireandstaplesitdown.A2pullswireoutfor20yards.A3shakeswireclearofobstructionsandputsinstaplesone-fourth,one-half,andthree-fourthswayalong.A1getsanothercoilandb ut tsit againstA 2'send ofthefirstcoilandstaplesbothendstogether.

A2andA3proceedasbeforeandsoonuntilthefirstrowiscomplete. A1,2,and 3carry15to 20staplesslungonacordovert heshoulder. Assoonasparty Ais clear, party B comesout.


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38 CONSTRUCTION AND EQUIPM ENT OF TRENCHES.B 1maulsin the anchor picket and the longpickets through thecenter of the coil every 5yards along the line.B2measuresdistanceandholdspicketsfordriving.B3suppliespickets.B 1shouldbeatallm an. Wherecoilsbu ttup againsteach othertheyarecrossedandthepicketisdriventhroughbothcoilsholdingthem together. Assoonasparty Bisclear party


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39ONSTRUCTION AND EQUIPMENT OF TRENCHES.bescrewed intoafirmhold without noise. Whentheenemyistooclose for this, various forms of portable obstacles in the natu re ofchevaux defrise areemployed. These aremade up at the depots,broughtforward throughth etrenchesand simply tossedoutin front,bydayorbynight.Several forms areused, such asthe regular chevaux de frise, theelongated sawbuck, and the tripod orhollow cube formed of steelanglerodsor plain rods. These obstacles are covered with barbedwire. Boardsfilledwithnailsarealsoused.71. When the enemy's bombers get into the approach trenchestheyattempttoworkdownthenundercoverofthezigzags,curves,ortraverses to attack one of the rear lines and provision should bemadebythedefensetochecksuchadvance. Itisbestaccomplishedbymakingtherear40yardsofanyapproachtrenchstraightandprovidingformachinegunandriflefiredownthestraightportion. Analternativearrangementistoprovideenfiladefiredownoneormoreofthezigzagsfromloopholesintheparapetofatrenchinrearcuttingthenecessaryslopingchannels tofirethrough. Provision mu stalsobemadeforblockingtherearmost40yardsoftheapproachtrenchatboth ends of the stretch by means of movable obstacles, such aschevaux de frise orother forms mentioned above, ke pt in a cornerofthetrench whenceth ey canbereadilypulled downinto positionbythelastmantoretire.72. Openingsforthepassageoftroopsthroughwireentanglementsaregenerally about 10yardswideand areplaced so that two beltsofwireoverlaptheopenings. (Pis.I , II , and IV.) Thecontinuityoftheobstaclemaybepreservedbyusinggatesorbarriersthatcanbequicklyopenedandclosed.Thebestplacefortheopeningsisattheflanksofthesupportingpointsbetweenthewireentanglementsaroundthesupportingpoints,and thosein theintervals. If theseopeningsmustbeplaced in theintervalsonaccountoftheterrain,th eymustbecoveredby theclosefireofsectionsoftrenchplacedimmediatelyinrear.

D EF EN SE O F B U IL D IN G S.73. I t is often advisable to in clu de substantial buildings inthe f iring l ine . Experience shows i t to be very hard to dislodgea determined defender from a properly organized bui ld ing . Ontheotherhand,buildingsinornearthefrontinvariablydrawmuchartil lery fire. For this reason a building should not normally beoccupied by day unless i t has cellars which can be improved to provide good bombproof cover, orsimilar cover can be made quite


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40 CONSTRUCTION AND EQUIPMENT OFTRENCHES.closetothehouseandconnectedwithitbycommunicatingapproachtrenches. Otherwise if the building has been put into a s ta te ofdefense a garrison should be detailed which will occupy it only atthelastmomentincaseofat tac k. Abuild ingisstrongestfordefensewhen i t has been knocked about a b i t. The defensive arrangementsshouldbeconcentratedonthefirstfloorandcellars;timespenton the upper stories is sure to be wasted . In the build ing itselftheworktobedoneis:(a) Reinforce the cellar roof if possible with concrete; i t mustbewellshoreduptoenableittocarrytheextraprotectionandalsothe debris which subsequent shellingw ill bring down upon it. (6) Loopholethewallsforrifle ormachinegunfire;th enearer theloopholeBare to the ground the better the protection afforded, butthereisariskoffallingd ebrisblockingth em .(c) Thickenwallsuptotheheightofthe loopholes. Thisthickening may be done by throwing earth up against the outs ide of thebuilding, or making a wall of gabions filled with earth or of earthbetween hurdles, 3feet clear of the wall of the building to serveas a shell burster. Building up inside with br ick rubble or earth in sandbagsisbetter, as loopholesnear the ground level and cellarwindows for machine guns can then be used.(d) Blocku pand loopholegroundfloordoorsandwindows.(e) Erect overhead cover over firing positions. This should beintheformofafalse roof,preferablyofconcrete,otherwiseofheavyrailsorverystouttimbersonverysubstantialtimbersupportsoronrails and g irders. Th is roof will p ro tect the firers from fallingdebris, and the moreth e houseis knocked about the strongerwillthe cover become.Inconnectionwiththedefenseofthebuildingtheremayalsobefiringtrenchesinfront ofitand on either flank, communicating bytrenchesw ithoneanotherand withth ebuilding,th ewhole formingpractically a small strong poin t of which the house is the keep."S l i t " trenches s ituated close beh ind the house and connectedwithitbyanapproachtrenchformausefuladjuncttothedefensivearrangements.

CONSTRUCTION OF TRENC HES.74 . Under fire. Thefirstobject is to get some sort of cover asquickly as possible for the firing l ine . The individual men s tarttodigpitsforthemselvesjustwheretheyarestoppedbytheenemy'sfire. Assoonas may bethese pits are then joined to form a con

tinuous firing t rench. This trench may form the u lt ima te frontfiringtrench and the covertrench besubsequently dug back of it,


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CONSTRUCTION AND EOOTPMENT OF TRENCHES. 41orit may become the cover trench and newfiringtrenches may bedug in front by push ing forward a t in te rvals . The question ofproper traverses for the final t rench should be considered in thespacingofthe firstconstructed pitsand in joining them up toformatrench. Itisdesirabletohavetraversesformed outoftheoriginalundisturbedground.If thefirstdugtrench is toform the cover trench the next stepafter completing it is to push forward T-heads to the front toformthefiringbays.The work of diggingth e individual firing pits will be begun bythe infantry troops generally with their intrenching tools. Troopsshould, therefore, be well practiced in digging themselves in bynightordaywiththesetools.Heavier more effective tools should be brought up to the firinglineassoonaspossibleandeveryplanforanadvanceshouldprovideforacertainnumberofdiggingtoolsinadditiontotheintrenchingtools accompanying the a ttack, and th is number should be supplementedasearlyaspossiblebyeverypickandshovelavailable.It may be necessary tow ait un til dark before a largenum beroftoolscanbe broughtup andseriousworkattem pted , bu titissometimespossibleunderthecoveringfireofartillerytodigacontinuoustrench by day. In anycaseeveryeffort mustbem adetogetgoodtrenchesdugassoonaspossibleand oneofthefirstthingstodoistoget some wire entanglement in front of the trench, asthisgives afeelingofsecuritytotheworkers.Duringthefirstdayortwothenewlinewillbebombardedheavilyandprobablycounterattacked. Ifthefronttrenchisconstructedinthe first instance very close to the enemy's l ine i t is part icularlyvulnerabletocounterattack,andiftheenemysucceedsinbreakingthroughthelineatatimewhentherearenodefensespreparedbehindit he may force aretirement ona large front. The constructionofsupport trenches.100 to 200 yards in rear of the front line and ofreservetrenchesshouldthereforebeproceededwithsimultaneously.75. At night.If the offensive open attack has to be given uptemporarily and the enemy is found in a prepared fortified line amoregradualand concealed method ofapproachhastobe adopted.Alineoftrenchesisconstructedinthefirstplaceatquiteadistance,say500to600yardsorevenmore,fromtheenemy'sfronttrench,theexactdistancedependingonthegroundandthefacilitiesforcover.This line is made fairly strong and complete before any furtheradvance is a ttempted. Then under cover of darkness or fog andperhaps of aheavy bombardment of the enemy's front l ine a newtrenchisconstructedatadistanceof200to300yardsfromtheenemy.


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42 CONSTRUCTION AND EQ UIPM ENT OF TRENCH ES.Fromthisline further advanceisusuallymadebysap. T he advantageofthismethodisthat before any attem pt ism ade to dig a linewithineasyreachofsmallcounterattacks,thereisacompletedlineready behind the new line, tostopfurther progressby the enemyifthe newlineiscounterattacked andbroken.76. I n order to get w ith in assaulting distance of th e enemytrenches,itisnecessarytopush outsapsfrom the firing trenches, atintervalsofperhaps20yards,andtheheadsofthesesapsmustthenbeconnectedb yacontinuoustrench calledth eparallelof departure.The construction of this parallel is a difficult task and can not beexpected to be accomplished in a s ingle night. The enemy's f ire andhand grenadescompelit tobeb uilt asasap. Oneofthe difficulties is main ta in ing the proper a lignment. The tendency is to dig in a broken or wavy line like tha t of the firing t rench . Thistraceisexce llent forth elatte ronaccountofitsfacilities forflankingfire,buttheprimeconditionoftheseveralshortelementscomposingthe parallel of departure is to face the objective, for the assaultingtroopswhostart from i t will goinstinctively straight forward.

Careful adjustment with th e use oftap e and compassisnecessarytogetgoodresults. The azimuth ofthe general direction ofattackisgiven to all whoha ve compasses forusewhen dust, night, orfogobscuretheobjective,andthetraceoftheparallelofdeparturemustbear90from thisgeneral direction.The profile of the parallel of departure must be tha t of anarrowtrench with banquette somewhat raised, continuous and withouttraverses . In this type only can the assaulting wave s tart in linewiththemenatonepaceinterval.Tokeeptheparallelclearofthedeadorwounded,theremustbearranged in sapsand other trenches some nichesi n which thedisabled canbeplaced temporarily.77. The construction of trenches should be preceded by carefulstaking out of lines and tasks assigned by measurement. Thisresults in an economy of time and prevention of confusion amongthe working parties. Otherwise parties will be digging at randomandsystemwillbelost.Newworkmustbegivenatonceitsfulld ep th. Theimprovementof a longtren ch une qua lly begun on itsdifferent sectionsgivesanopportunity for laziness and loss of t ime. In daylight th e officershould show th e chief ofeach workingp arty in m inute detail, theworkassigned tohispa rty, hav ehim marki t outhimself and determinethemenneeded; thenatnightformthemandsendthemupin succession. The men should have eaten before starting, for thearrivalofamealatnightisanunfailing pretextforleavingthework.


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CONSTRUCTION AND EQUIPMENT OFTRENCHES. 437 8 . Placing the workers and executing the work.The men aredividedintoworking

Notes on the Construction and Equipment of Trenches

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