Historical Document · 1952
The Operations Research Office's 1952 Project BALANCE memorandum that analysed combat ranges and hit probability and argued for a weapon delivering several projectiles per aim. The Hyper-Burst Mechanisms dive starts its history of salvo and burst fire here.
UNCLASSIFIED AD NUMBER AD-000 346 NEW LIMITATION CHANGE TO DISTRIBUTION STATEMENT - A Approved for public release; distribution is unlimited. LIMITATION CODE: 1 FROM NO PRIOR DISTRIBUTION STATEMENT ASSIGNED AUTHORITY USAMSAA; MAR 23, 1973 THIS PAGE IS UNCLASSIFIED u~ CHNICAL MEMORANDUM ORO- T -160"" T 383 H57 1952 UNCLASSIFIED Operational Requirements U .S. ARMY M!LITARY HISTORY INSTITUTE CARLISLE BARRACKS, PA l 70 13· 5008 INFANTRY HAND WEAPON OPERATIONS RESEARCH OFFICE • The Johns Hopkins University By Norman Hitchman Stat istical Analys is by Scott Forbush and George Blakemore Jr. This document is now unclassified, as shown on the cover or title page, and all other markings found on any pages are obsolete. If any photocopies are made of this document, all markings, other than UNCLASSIFIED, on each page should be obliterated so that there is no misunderstanding of the current classification of any information derived from it. I ARMY \i C L SLE Operating Under Contract with the DEPARTMENT OF THE ARMY For an Ay COLLEGE ACKS, PA... Received: 19 June 1952 The contents of ORO publications, including the conclusions and recommendations, represent the views of ORO and should not be considered as having official Deportment of the .Army approval, either expressed or implied. ARMY WAR CCllEGE LIBRARY ~5~~- ---------- ---------------; Actessioo Number - - - -------------------- · A WC Fonn 1 Army---CGSC-P2-0236- 9 Aue 51-25M 29 May 60 .... ~ -~--·· ·-··· contains information affecting the notional defense of the United States within the meaning of the Espionage Lows, Title 18, U. S. C., Sections 793 and 794 . The transmission or the revelation of its contents in any manner to an unauthorized person is prohibited by law. Unc\assit\ed :r 1 ' ~- ~ ... . : DOV.!NGRAOE~ AT 3 YEAR INTE~VALS: D~~tA$.~,,-. '"- .; . 4 ,-~A !2 YL:;~.~s. DOD Dill 5200.10 :( ( THIS IS A WORKING PAPER Presenting the considered. re suits of study by the ORO staff members responsible for its preparation. The findings and analysis are subject to revision as may be required by new facts or by modification of basic assumptions. Comments and criticism of the contents are invited. Remarks should be addressed to: ' The Director Operations Research Office The Johns Hopkins University 6410 Connecticut Avenue Chevy Chase, Maryland L1 BR;:\~1"' ( ARMY WAR COLLEGE CARLiSLE BARRACKS, PA. UN&[ ~ trtt OPERATIONAL REQUIREMENTS FOR AN INFANTRY HAND WEAPOli by NonrHIIt A. Hltdtman Statistical Analysis by · Scott E. Forbush George J, Blalcemore, Jr. Of what should a rifle be ·capable in baHie today? Since there is a limit!as to how accurately the infantryman fires, can one increase hits by giving him a rifle with new operational charact•istics? ORO's Project BALANCE studied this by talcing data on haw often, and by haw much, ·riflemen missed targets (as well as the distribution of hits) at different ranges, by taking data on the ranges of engagement In batt-le, and by talcing_data on the physiological wound effects of shots with differing ballistic characteristics. · The recommendation is made that Ordnance prQCeed to determine the technological feasibility of a weapon with oper~ing characteristics analyzed in this memorandum. This follows front conclusions which ore listed only sketchily below: >..c ., c .... .X. Cl 'C • Hit effectiveness using the ~1 is satisfactory only up to 100 yards and declines very rapidly to low order at 300 yards, the general limit for baHiefield rifle engagements. · • A poH*n-dispersion principle in the hand weapon would ten'd t9 compensate for human aiming errors and increase hits at ranges up to 300 yards. Missiles, smaller cal-iber than now standard, ·could be used without loss· in wounding effects and with • lethality logistical advantage, and a great increase in hit could be effected by using toxic missiles. ~ Ill Abatract page from: ..a UNCLASSIFIED ORO-T-160 !~ ·· ~ 38 ,, Log No. __......:...;;:..~-·····-----·-·-Copy No..........................~~...................... hell+ lO!)pp, !11 Figs., U TablesJ Received: 19 June 1952 Proiect BALANCE This Document contains information aHeding the National Delense ol the United States within the meaning ol the Espionage Law.r, Title 18, U.S.C., Sedions 793 and 794. The transmission or the revelation ol its contents in any manner to an unauthorized person is prohibited by law. THIS ABSTRACT IS 9F A WORKING PAPER Presenting the considered results of study by the ORO staff members responsible for its preparation. The findings dnd analysis ore subject to revision a:. may be required by new facts or by modification of basic assumptions. Comments and criticism of the contents are invited. Remarks should be ad· dressed to: The Director Operations Research Office The Johns Hopkins University 6410 Connecticut Avenue Chevy Chase, Maryland ilC T ecbnicallttemorandum ORO·T·l60 ,,.-OPERATIONAL REQUIREMENTS FOR AN INFANTRY HAND WEAPON by Norman ~itchman Statistical Analysis by Scott E. Forbush George J. Blakemore, Jr. LIBRARY ARMY WAR COLLEGE CARLISLE BARRACKS, PA.. Received: 19 June 1952 Project BALANCE OPERATIONS RESEARCH OFFICE, ~~-· ·-·The Johns. t·lopki~s Univ;;.;iiy: Ch~ry Chase, Maryland Copy Log No. G'l of 250 21938 PROPERTY OF US ARMY Unclassified .• U:D 38"3 HS7 193:2 Published November 1952 by OPE RATIONS RESEARCH OFFICE 6410 Connecticut Avenue Chevy Chase, Maryland classifiel1 •.,. .....! [ •·--~~~~~~~-~~~~~---" C'PEP.'fY a:;;· U.S. ARM' Unclassified ACKNOWLEDGMENT The author gratefully acknowledges the valuable assistance given b...y Col. E . M. Parker, Project Chairman, in the preparation of this study; especially were his paraphrases welcomed, for they crystallized areas of thought where otherwise the author would have faltered. vii _- 1 Unc\ass\1\eO il€11, N lf&IJI rt'K SfCQ Unclassified CONTENTS Page ABSTRACT iii ACKNOWLEDGMENT S vii SUMMARY Purpose- Assumptions- Discussion - Conclusions Recommendations. OPERATIONAL REQUIREMENTS FOR AN INFANTRY HAND WEAPON Introduction 1 5 COMBAT CASUALTY STUDIES Former Studies- Lethality of the Rifle- Rifle Bullet Hits as a Function of Range in CombatMan-Rifle Operations Studies . 7 TERRAIN VISIBILITY STUDIES Range Requirements and Tactical Employment of Hand Weapons- Map Analysis. 10 THE RIFLEMAN AND HIS WEAPON Marksmanship: Tests and Analyses- The Pattern Salvo Weapon- Full-Automatic Fire-Wound Ballistics: Missile Caliber, Mass, and Velocity. 15 LETHALITY Weapons in General- The Rifle- Comparison of an Ideal Dispersion Automatic with M-1 SingleShot Fire -Can Lethality Be Increased? 25 THE DISPERSION WEAPON Basis of Issue (T /O&E)- Training- Design Feasibility. 31 urrc asstTiea ~II'" ' ix • 11: J!CI!I IRIAt:sr I flniii!Y SF(I[J iW.MA'JioN nc\ass\1\ed CONTENTS (Continued) Page A THEORY FOR DETERMINING RELATIVE EFFECTIVENESS OF DIRECT FIRE WEAPONS Method Used. 35 CONCLUSIONS 40 RECOMMENDA TIONS 40 BIBLIOGRAPH Y 4Z APPENDIX Analysis and Application of Results of Rifle-Range Tests. 43 FIGURES Comparison of Battlefield Visibility in Korea 1. and Ranges of Employment of the M-1 Rifle. Frequency Distribution for Ranges of Continuous Visibility for Terrain Classes A, B, and C. 12. Method Used in Measuring Range of Visibility on Maps. 14 4. Marksmanship Using the M-1 Rifle. 17 5. Comparison of Lethality per Aimed Shot or Burst for the M-1 and the Salvo Automatic. 2.8 Rifle Marksmanship , Battlefield Visibility, and Hit Probability in Combat. 37 2.. 3. - 10 A' ~ 6. 7. Theoretical Distribution of Hits as Function of Range for M-1 Rifle and a Salvo-Type Hand Wea38 pon for Terrain Classes A, C. 8. Relative Effectiveness of M-1 Rifle and Salvo Automatic for Terrain Classes A, C. X ~lliU S&Cifl :APGIMifi!N 39 Unclassified CONTENTS (Continued) Page TABLES 1. Computed Distribution of Hits as Function of RangeR. 2. Relative Effects of M- 1 Single-Round Fire and Salvo Fire as Function of Range for Terrain Classes A and C. nclassi·fied xi •;;!""" IECIET utt ami!! • 36 38 A' 2 .·~-- ··}~~- t_!. '!: . - -~~ ":_-. ,. .. • SUMMARY PURPOSE The study reported upon in this memorandum was undertaken for the purpose of determining the desirable operation'a l char acteristics of a general purpose infantry hand weapon . ASSUMPTIONS It has been assumed that it is desirable to increase in both number and rate the hits which may be inflicted on the enemy by aimed small arms in the hands of the infantry. It has been further assumed that it is desirable also to increase the mortality of wounds caused by these hits. DISCUSSION In this examination of the basic infantry weapon , the rifle, two commonly accepted considerations or premises were carefully scrutinized, and thei r bearing upon infantry operations evaluated: 1) the time taken to hit enemy man targets is vital in that hits should be inflicted as early and at as great a range as possible; and l) these hits should inflict significant injuryshould be at least immediately incapacitating (in some circumstances, lethal). The findings are generally affirmative with respect to both propositions. Study of combat records of operations, as we ll as field investigations of the man-rifle combination, shows that much is to be gained by increasing the hit capability of aimed rifle fire at the common battle ranges, and that increasing the severity of the hits is also to be sought. How men actually use the rifle in combat, the .ranges of engagement most frequently recurr~ng in battle, how terrain limits intervisibility of opposing firing ORO-T-160 . U nc\ assi~, - .,_WIMI.....'.,.... 1 lines, and what is required ballistically to create physiologically desirable wound effects on the enemy, are factors which have been analyzed for the purpose of determining the operational requirements of a general purpose hand weapon. Study of the various factors involved has yielded a number of independent but related and consistent determinations. Synthesis has permitted comprehensive evaluation of the combat actions bearing in concert upon effective employment of the hand weapon. Battlefield visibility data show why combat rifle fire is actually so limited in range by normal terrain obstructions to the line of sight as rarely to exceed 300 yd. Studies of the manner in which gunshot wounds are incurred in battle suggest that lesser-included ranges are in reality the important ones. Measurements of marksmanship show that performance is of a very low order beyond a range of 300 yd. Wound ballistic data offer convincing evidence that small caliber, high velocity missiles may be used profitably at such ranges, without loss in wounding effects and with significant logistical gains. The mutually confirmatory nature of the several findings goes far to explain present rifle operations, and to suggest the desirable characteristics for a general purpose infantry hand weapon. The conclusions which follow have emerged. CONCLUSIONS A' 1J 1. The ranges at which the rifle is used most frequently in battle and the ranges within which the greater fraction of man targets can be seen on the battlefield do not exceed 300 yd. 2. Within these important battle ranges, the marksmanship of even expert riflemen is satisfactory in meeting actual battle requirements only up to 100 yd; beyond 100 yd, marksmanship declines sharply, reaching a low order at 300 yd. 3. To improve hit effectiveness at the ranges not covered satisfactorily in this sense by men using the M-1 { 100 to 300 yd), the adoption of a pattern-dispersion principle in the hand weapon could partly compensate for human aiming errors and thereby significantly increase the hits at ranges up to 300 yd. 4. Current models of fully automatic hand weapons afford neither these desirable characteristics nor adequate alternatives. Such weapons are valueless from the standpoint of increasing the number of targets hit when aiming on separ'ated man-size targets . Unclassified ,.sa:eP!fll[f .... ORO-T-160 5. Certain of observed in the manufacture of current rifles and ammunition can be relaxed without significant losses in over-all hit effectiveness. 6. To meet the actual operational requirements of a general purpose infantry hand weapon, many possibilities are open for designs which will give desirable dispersion patterns (and accom· panying increases in hit probability) at the ranges of interest. Of the possible salvo or volley automatic de signs, • the small caliber, lightweight weapon with controlled dispersion char· acteristics appears to be a promising approach. (Low recoil of a small caliber weapon facilitates dispersion control.) 7. To create militarily acceptable wound damage at common battle ranges, _missiles of smaller caliber than the present stand· ard .30 cal can be used without loss in wounding effects and with substantial logistical and over-all military gains. 8. A very great increase in hit lethality can be effected by the addition of toxic agents to bullet missiles. RECOMMENDATIONS 1. It is recommended that the Ordnance Corps proceed to determine the design or technological feasibility of developing a hand weapon which has the characteristics cited in this analysis, namely: a. Maximum hit effectiveness against man targets within 300 yd range. (This does not mean that the weapon will be ineffective beyond this range.) b. Small caliber (less than . 30). c. Wounding capability up to 300 yd at least equivalent to the present rifle. d. Dispersion of rounds from salvos or burst controlled so as to form a pattern such that aiming errors up to 300 yd *Current military usage of the two words salvo and volley is confused. By "salvon the Navy and Air Force generally mean, respectively, the simultaneous discharge of several pieces, or the simultaneous release of a number of bombs; the Army usually employs the word to indicate the successive firing of several guns within a single command unit. "Volley" is commonly taken by all services to mean the simultaneous firing of a number of rifles or guns, with the exception that the artilleryman often applies the word to the independent (unsyncbronized) firing of a certain specified number of rounds by each of several associated. pieces. What is discussed here and in the following pages is either a simultaneous, or a high cyclic rate, burst, with the number of rounds per burst automatically set rather than dependent upon trigger release, In the former design, con• trolled nv.tation of the rifle muzzle would provide the desired shot dispersion or pattern; in the latter, the scatter would be obtained and controlled by multiple barrels, a mothe~ daughters type of projectile, or projection of missiles in the manner of a shotgun • • ORO-T-160 ,. \~.d~~rtJet1 Mtillf S!CRE I IMlliMAIIC4 3 SE~R.-;-m !leN FORMATION Unclassifi will be partly compensated, and hit effectiveness thereby increased for these ranges. 2. As one possible alternative to the current "volume of fire" {fully automatic) approach to the problem of increasing the effective firepower of infantry riflemen, it is recommended - subject to tentative confirmation of design feasibility-that a rifle incorporating at least in principle the military characteristics here proposed be manufactured for further and conclusive test. 4 Unciass!Jied ORO-T-160 ~~r~~--:::"x=IS~EEil~Rai~I~..~·I6i"llilii:O~NL...._ • nl lit•1ed Un· Lr.asst lject OPERATIONAL REQUIREMENTS FOR AN INFANTRY HAND WEAPON iNTRODUCTION The subject of this study is of a basic nature for it applies to the basic weapon of the basic branch-the rifle carried by the infantry. Because the hand arm offers certain capabilities not duplicated by any other means, and because it is basic to the whole weapons system, the effectiveness of that weapon in battle is a subject of first importance in any general consideration of the whole fire system. It follows that any study directed toward a comprehensive examination of the aggregate of weapons for the purpose of designing and proportioning a .. balanced" system (the mission of Project BALANCE) may logically take a beginning with this basic ground weapon. Such an approach is, moreover, timely at the moment in the sense that the NATO is confronted now by an urgent requirement for standardization of a general purpose hand weapon for the infantry. Thus, any information which may be cogently pertinent to such weapons will have a bearing on an immediate problem of some moment. The study here presented has been carried out not only in full recognition of the importance of improving the effectiveness of infantry, but also in growing awareness that the task-even though so basic in nature-is an exceedingly complex one. · The effort has thus far been only preliminary. Limited time, and inadequate knowledge of basic unit operations in combat, have restricted the degree to which the whole problem might be examined. Consequently, no complete solution is offered by this memorandum; rather, some analytical findings are presented, which suggest the principles governing certain measures which could be undertaken to improve infantry effectiveness with respect to aimed rifle fire. This memorandum bears directly upon the importance and the use by infantr y of aimed small arms fire in the front line ORO-T-160 unclassified •::~" ' H f 3[I .amn 2!!01 5 - .. sKbkli I §li(llil 'NfRRMATIRN sifi tactical fire fight, but does not consider expressly the importance, the techniques or the effects of unaimed .. covering fire" delivered by small arms. The reason for directing the study effort toward aimed fire is that the common a-rm of the infantry, the rifle, is designed primarily for the aimed fire role; that is, the weapon is designed expressly to afford a capability of directing missiles at observed man-targets with high inherent precision, in both offensive and defensive action. Delivery by such a weapon of covering fire to neutralize or pin down the enemy and permit friendly maneuver is tactically useful, but nonetheless amounts to a secondary role for which design has provided only incidentally. The important question at band, therefore, is not so much connected with the varying actual use of the present firearm as with the need of the infantry to engage the close enemy effectively by the use of aimed rifle fire, and with the feasibility of incorporating in the rifle of general issue the capability of answering this real requirement. Recent ORO investigations in Korea have shed some light on this subject by indicating quantitatively the comparative importance of aimed and unaimed fire as related to offensive and defensive operations. Generally, aimed fire plays a more important part in defense than unaimed or volume fire, whereas in the offensive, the reverse is true Almost irrespective of the part played by the supporting weapons before or during the final phase of close combat, the decision in each small tactical battle rests ultimately in large measure with the infantryman and his ability to use his hand weapon effectively. If hand-to-hand fighting develops at all, decision thus rests almost entirely with the infantry in this last time -phase of the tactical situation. To attach importance to this aspect of battle is therefore logical, and the a~tempt to maximize the capability of infantry in this role cannot be misdirected effort. The study has yielded suggestions for increasing infantry effectiveness by improving the effects of aimed rifle fire. It appears almost certain that future large-scale ground operations will involve a numerically superior enemy and necessitate, at first, a defensiv'e strategy on our part, Morever, frequent attempts to overrun infantry positions, with attendant close combat, are to be anticipated. Thus, to increase .~ac.h · infantry man's capability with respect to defensive rifle ffr ·e becomes highly desirable. In the light of such considerations as these, it appears correct to assume that: 1) it is desirable to increase in both number and ORO-T-160 .. I SEERET :a:; 4 .. I SECURITY SECI!T rate the hits" which may be inflicted on the enemy by aimed small arms in the hands of the infantry; 2) it is also desirable to increase the mortality from wounds caused by these hits. The research effort has included examination of casualties of past wars, studies of terrain as it limits battlefield visibility, determination of the marksmanship of men, wound ballistics requirements, actual use of the rifle in combat, and other considerations bearing on military operational requirements for the general purpose hand weapon. The determinations arrived at from the study of present rifle fire and its effects are presented in the following sections. COMBAT CASUALTY STUDIES '· Former Studies Earlier work done by ORO on the defense of the individual in combat,1 and a preliminary study of the offensive capabilities of the rifle/ yielded definite indications that rifle fire and its effects were deficient in some important military respects, and that further study of the problem would be necessary fully to establish the facts. In these former studies it was found that, in combat, hits from bullets are incurred by the body at random: regional distribution of bullet hits was the same as for fragment missiles which, unlike the bullet, are not "aimed." Further, it was found that exposure was the chief factor responsible for the distribution of hits from bullets and that aimed or directed fire does not influence the manner in which hits are sustained.' Stated briefly, the comparison of hits from bullets with those from fragments showed that the rifle bullet is not actually better dil,·ected towards vulnerable parts of the body. The discovery of these facts, along with evidence of prodigious rifle ammunition expenditure per hit, strongly suggested the need to extend the study of the rifle problem. The facts known a.t this point also prompted one to regard with some dubiety the employme~t of the present, highly accurate, precision-made rifle as a general purpose infantry weapon. It should be noted~ ..·however, that complete verification would not suggest elimination of a precision long-range rifle to be used . 'Footnote numbers refer to publications listed in BibliogJ"aphy . Multiple hits on the same target are much less to be desired than a large number of targets hit. ORO-T-160 .. Unclassified u II 5[ERE T "JiS'MtUIP* 1 .. Si!t!l I sF c8[T INFORMATION by some men highly skilled and selected for specialist opera tions, e. g., snipers. Lethality of the Rifle As for the combat importance of hits from rifle bullets as compared to other weapons in the ground system, historical studies show that bullets have accounted for 10 to 20 percent of all hits from all ground weapons in most battles, campaigns, and 4 wars of this century. Although these figures qualitatively provide a mea~ure of the relative capability of hitting the opposed infantryman, they do not disclose capabilities. with respect to severity of mJury. Of these two factors (simple wounding and extent of injury) which characterize weapons effects, not much is known about either in the sense of cost versus effect because ammunition expenditures and corresponding casualty-produ cing effects are not usually known with precision. On the other hand, aside from the closely related machine gun, the rifle is the most lethal of all conventional ground arms: its lethal index (ratio of kills to hits) exceeds 30 percent, putting it above other weapons in capability of inflicting severe injury. • The lethal index of the machine gun, of course, exceeds that of the rifle because multiple hits increase over -all lethality. For bullet lethality, the 30 percent figure given for the rifle would be the closest approximation to single round lethality for all ranges in battle . A' I Rifle Bullet Hits as a Function of Range in Combat Knowledge of the ranges at which hits have been incurred in past wars is sharply limited. Since this parameter is almost indispensable to the military specialist or operations analyst in determining weapons effects, it is astonishing that greater efforts in the past have not been directed toward gathering information of this kind in combat operations . •In thie analysis, the figure 30 percent refers only to enemy weapons of World War II type but since enemy rifles did not differ greatly from our own, the lethal index value should approximate that of the M-1 rifle. Strictly, lethal refers here to the bullet, rather than the rifle, which is the launcher. What is meant is that a larger fraction of the total bullet hits results in death than from hits from any other weapon. The explanation does not lie in the manner in which rifle bullets are directed, since data show that bullet hits occur on the body at random just as do hits from fragmenting projectiles and therefore their relatively high lethality is not connected with any bias in their distribution over the body. The reason appears to be c onnected with the higher (and more nearly constant) energy, on the average, than other missiles since they are discharged at short ranges. Fragments, however, vary in energy from a maximum to zero, with the mean value being relatively low because of the preponderance of small fragments per missile burst and because of the rapid deceleration of particle velocities with range. ORO-T-160 .. w EEERET $ SECURITY !EER&T 1)'$8"0!:9" Unclassified md de ry- ,f 1ry) ther res .own ed Lmd ., ds y. llld 1ges ldisrthe .er al es Only two studies exist which have reference to bullet hits as a function of range in battle, and they are based on indirect and possibly inaccurate measurements. Oughterson 5 analyzed experience on Bougainville in World War II and found that, of those cases studied, almost all rifle bullet hits were received at ranges less than 75 yd.• The Surgeon General recently examined the wounded in Korea, and from a sample of 109 rifle bullet hits suffered among members of the Turkish Brigade, the mean range for these hits was found to be just over 100 yd. 6 It was noted, however, that most of the hits occurred at ranges within 300 yd and in a later section of this report these data along with data on battlefield visibility will be given more extensive treatment. Man-Rifle Operations Studies The British AORG during World War II, and ORO in FECOM, have both attempted to study part of the man-rifle complex by interviewing experienced riflemen on their use of the weapon in offensive and defensive combat actions. The British examined officers and NCOs who had experience in the ETO 7 and ORO examined men with experience in Korea. 8 The agreement of the two independent studies is striking . For attack and defense in European actions, it was found that about 80 percent of effective rifle and LMG fire takes place at less than 200 yd and 90 percent at less than 300 yd, according to the estimates made by the men interviewed. About 90 percent of the LMG fire was at less than 300 yd. Of 602 men questioned about use of the M-1 rifle in Korea, 8 7 percent said that at least 95 percent** of all their firing was done at targets within 300 yd range (day time offensive fighting) , R For day time defensive fighting, 80 percent of the men said that rifles were used at 300 yd or less. Figure 1 shows the frequency in which rifles are used as a function of range, based on responses of interrogated infantrymen. The approximate correspondence of the curves in the Figure indicates that the use of the rifle is to at leas.t some extent dependent upon battlefield terrain features as they affect visibility."*"' Although it is freely acknowledged that the use of data derived from judgments of the men about the use of their basic arm may be subject to question, the validity of the •This figure is perhaps atypically low because it refers to jungle fighting in which >rt :e L60 ,.,.visibility was abnormally restricted. The ' men were asked to give the outside limit of 95 percent of their firing in order to eliminate those rare shots which might be fired at long ranges without expectation of ***hitting the target. See section on battlefield visibility. ORO-T-160 IJnc assified '= nEuRITY SEt RET INin :s:s 9 optnton survey has been substantiated by a more recent Korean study conducted in combat areas. 9 Also, as mentioned earlier, the analysis made by AORG tends to support the conclusion that ---Probability of seeing a man target* - Frequency of employmel)t of rifle, daytime offensive action* • • • • Frequency of employment of rifle, do yt ime defensive act ion* *At and beyond Range R t- z w u 0:: w a.. • __..- Unoimed and /Aimed Fire includ11d ~ • • 0 100 200 • 300 400 500 RANGE (YO) Fig. 1-Comparison of battlefield visibility in Korea and ranges of employment of the M-1 Rifle. A. I the infantry basic weapon is actually used, on the average, at shorter ranges than commonly believed. TERRAIN VISIBILITY STUDIES Range Requirements and Tactical Employment of Hand Weapons Despite the important role of infantry support weapons (artillery, tactical aviation, armor, and others), the entire ground weapon system hinges in many important ways upon those weapons which depend for their effective employment upon ground observation of the target . These are the direct-fire and observed-fire weapons; they are elemental. basic, and indispensable to the infantry-artillery-armor team. 10 Unc assified Jli!Si4 4 ORO-T-160 'fRWRITY SE(REIINFORMATION" For infantry, the basic direct fire weapon is the rifle -it is the common denominator upon which the entire fire system is designed, both physically and tactically. Yet all direct-fire weapons suffer a major weakness in that essential observation for their effective employment may be obscured by weather conditions, prevented by darkness or-more importantly and quite unavoidably-interrup ted by terrain features . This interruption of the line of sight is one of the principal military effects of terrain, for the ranges at which points on the ground are intervisible are related to the employment and general effectiveness of these direct-fire weapons. Accordingly, terrain limitations to continuous visibility on the battlefield should dictate to a considerable degree the actual design and employment of direct-fire or observed-fire weapons. A study of this subject which was undertaken by Project BALANCE and which is covered in detail in a separate report, 10 has yielded formulary expressions for the relationship between the opening range of engagement for riflemen and the range at which man-targets can be seen. Particularly with respect to the rifle, the study is basic in its concept and possibly, for the first time, data have been obtained which constitute a reasonable quantitative basis for determining the actual range requirements and tactical employment of a general-purpose hand arm. Because of the importance of these findings to the infantry weapons problem, they should be studied carefully in conjunction with the work presented here on operational requirements for an infantry hand weapon. Map Analysis 1- ons l."e Topographical map studies of a number of large scale ( 1 :25,000} maps of various countries in the world have shown that it is possible to predict, with reasonable accuracy, the probability of being able to see continuously for a given distance from a random point within the area. 10 For the infantry study, the procedure used in the map analyses was to measure the continuous ranges of visibility between infantrymen, with the position of one man (the defender) being at ground level (foxhole or prone} and the approaching enemy being an erect human target five feet high. This factor was chosen to set realistic limits on the range of 60 nrn~rassrfieang ORO-T-160 forces. The 11 saUkil I §[(A&I INWRMATION +n ' ilemex 5i(I'J 'Nf0 RMATION validity of the map readings was verified by actual terrain measurements• and the findings are in general agreement with limited combat data from the Korean experience and ETO experience during World War II .** From the map study, it was found that all the types of terrain so far considered fall into one of three categories which are illus- 0 z LIJ LIJ •• "' u. •• 0 •• >- 0.5 •• •• •• • •• • 1_J m 0.4 < ::0 0 a: 0.3 a. 0 1000 500 1500 R (YO) Fig. 2-Frequency distribution for ranges of continuous visibility for Terrain Classes A, B, and C. {Probability of seeing man-targets at ranges greater than R yards from o random point within the area covered by the map analysis.} *Tests were conducted on the battlefield area of Gettysburg in which a small party of ORO ana.lysts checked map predictions by actually walking over the terrain in accordance with the map bearings and measuring the distance of intervisibility. In every instance, distances of continuous visibility were found to be less than the distances predicted by map measurement because of terrain features and obstacles not shown on .. maps. Map readings were considered, therefore, to represent maxima. The mean ranges of visibility from map analyses of Korea and Normandy show remarkable agreement with limited combat knowledge of ranges of engagement between riflemen and between tanks. In Korea, the frequency of ranges for bullet hits agreed with the frequency of ranges for visibility. For World War II tank battles, both Peterson of Ballistics Research Laboratory and ORO (Ref. 10) have shown that ranges of engagement for tanks correspond with ranges of visibility in the battle areas as determined from map analysis. These two samples of combat data tend to validate the use of the map data for predicting range requirements. c\ iiiiltRn ORO-T-160 i iCR&t••'-., i 1 ~- trated by the three curves in Fig. 2 . The frequency distribution for Type A terrain is typical for a country like the Saint-Lo area in Normandy, where visibility is sharply limited by the masses of hedgerows, small cultivated fields, orchards, and the nature of the terrain itself. Type A also describes rugged, mountainous terrain like Korea. The distribution curve for Type C describes relatively open country where the topography is gently rolling and large, open, cultivated areas exist. Type B is intermediate between the two extremes cited and describes an average type of cultivated countryside. The importance of these data to the infantry study is related to the range requirements for infantry weapons and, as shown in Fig. 2, 95 percent of all observations include ranges which are much less than the range capabilities of many of the infantry direct fire weapons. The implication that such weapons may be over-designed is appreciated when it is considered that the rifle alone has a maximum range capability of 3,500 yd. The following description of the procedure used in the map study is presented so that the practical application of the data may be recognized. )0 on ;e- &0 Figure 3 shows diagrammatically a corner section of a 1 :25,000 map. The method of measurement was adopted from a suggestion by Peterson of Ballistics Research Laboratory who used map grid lines as guides for sampling any given terrain. The analysis of each map is begun at Point A (northwest corner}. Proceeding along the east-west grid line , the distance is measured from the edge of the map to the point where an erect (five feet) infantryman would just be obscured from the sight of a defending prone infantryman at Point A . In this case, the crest of a hill (contour) is the factor which obstructs visibility. After recording the distance A to B, the next point of obscuration is measured by proceeding along the grid line from Point B to Point C where a railroad embankment interrupts the line of vision. Distance BC is then recorded and so on along the grid line to the far edge of the map. It will be noted that a house or building limits visibility at Point D and woods limit vision at Point E. After all horizontal grid lines are measured in this way, the same method is used on all vertical grid lines. Then all the obscurations from one map are used to plot a frequency distribution. Examples of such frequency distribution have been given already in Fig. 2. ORO-T-160 . r .. l, ~ncl , J :asstrted Sji" "' §[(I[J ltti • nP 13 usu'nx i &ERET 'f. 0 • J , ! ~ ,..., w _.,... ~... r .. ''l!$ . .... f~ l}i r , .. .,I ..:/ Although the fr-eque-nt!:Y distril:!.~tio~ -~~r:~_es yield predictions as to the probability of seeing man targets at Range R, from any random point on the terrain, it may be argued that infantryme n are not randomly located along the front but actually take up positions which have been selected for point of advantage (for example, high ground in the defence). So far as this is true for small units such as squads and platoons especially in defensive positions, such biases as a result of the placement of men are not systematic , and when division or corps fronts are considered , the density of men and their positions across a broad front can be considered to be more Map \ \ \ \ \ \ .. \ \ \ ~ '-/ \ '\ I I I I \ \ JL 3 Fig, 3-Method used in measuring range of visibility on maps. Starting at the northwest corner of the mop one looks from the point A, where the first hori zontal grid line begins, along that grid I ine to the point B where, because he has gone over the crest of a hill, the standing infantryman (the target) ceases to be visible. The distance AB is measured and recorded. Next, starting from 8, one finds that the target is continuously visible until the railroad embankment at C causes obstruction to view; the distance BC is then measured and recorded. Similarly, starting from the top of the embankment, it is clear that there is no obstacle until one reaches the house at D; CD is measured and recorded. Next the distance DE is recorded; then, starting from the eastern edge of the wood, the distance to the next obstruction is measured; and so on across the map to the right margin. After all horizontal grid lines have been followed in this way, one starts again at the northwest corner and reads from F dow~ the first vert ical grid line and all the other grid lines. All the readings obtained in this way are used to plot a frequency distribution. Figures 2 through 7 are examples of such frequency distributions . SE.. S!CRE I INfdk&a: 4 9 ~--~s:Ec~~~~~tv~S~E~(~Kitt~i~INIIIS!Itll-. as :tnlS .gh ch iases :n re ne ne or less uniform. Thus, in relation to terrain, their position is more nearly random . Also, no systematic selection of ground is permitted either side during a battle, since position, which is fluid and constantly changing, is dependent upon the whole battle situation and not just upon ground features. Therefore, the random selection on a map of a battlefront in any given terrain should predict the actual ground condition of the battlefield. In general, it is felt that men move in battle in a more or less random manner, so the data obtained in the visibility study are reasonably valid for predicting the probability of seeing targets over any area, particularly since the method used measured the type of movement used by troops in battle, that is, from cover to cover. Employing this method, map studies of Canada, France, Germany, Korea, North Africa, and the US, to a total of some 18,000 readings, showed that 70 percent of the ranges at which an erect human target can be seen by a defending prone rifleman are less than 300 yd (and that 90 percent are less than 700 yd). Since range requirements exert a considerable if not dominating influence upon such characteristic s as weight, caliber, and missile velocity, the data from the map analyses have a very important bearing upon the design of an infantry hand weapon . C