C-WAM 4 (Breakpoints)

A breakpoint or involuntary change in posture is an essential part of modeling. There is a breakpoint methodology in C-WAM. According to slide 18 and rule book section 5.7.2 is that ground unit below 50% strength can only defend. It is removed at below 30% strength. I gather this is a breakpoint for a brigade.


Let me just quote from Chapter 18 (Modeling Warfare) of my book War by Numbers: Understanding Conventional Combat (pages 288-289):

The original breakpoints study was done in 1954 by Dorothy Clark of ORO [which can be found here].[1] It examined forty-three battalion-level engagements where the units “broke,” including measuring the percentage of losses at the time of the break. Clark correctly determined that casualties were probably not the primary cause of the breakpoint and also declared the need to look at more data. Obviously, forty-three cases of highly variable social science-type data with a large number of variables influencing them are not enough for any form of definitive study. Furthermore, she divided the breakpoints into three categories, resulting in one category based upon only nine observations. Also, as should have been obvious, this data would apply only to battalion-level combat. Clark concluded “The statement that a unit can be considered no longer combat effective when it has suffered a specific casualty percentage is a gross oversimplification not supported by combat data.” She also stated “Because of wide variations in data, average loss percentages alone have limited meaning.”[2]

Yet, even with her clear rejection of a percent loss formulation for breakpoints, the 20 to 40 percent casualty breakpoint figures remained in use by the training and combat modeling community. Charts in the 1964 Maneuver Control field manual showed a curve with the probability of unit break based on percentage of combat casualties.[3] Once a defending unit reached around 40 percent casualties, the chance of breaking approached 100 percent. Once an attacking unit reached around 20 percent casualties, the chance of it halting (type I break) approached 100% and the chance of it breaking (type II break) reached 40 percent. These data were for battalion-level combat. Because they were also applied to combat models, many models established a breakpoint of around 30 or 40 percent casualties for units of any size (and often applied to division-sized units).

To date, we have absolutely no idea where these rule-of-thumb formulations came from and despair of ever discovering their source. These formulations persist despite the fact that in fifteen (35%) of the cases in Clark’s study, the battalions had suffered more than 40 percent casualties before they broke. Furthermore, at the division-level in World War II, only two U.S. Army divisions (and there were ninety-one committed to combat) ever suffered more than 30% casualties in a week![4] Yet, there were many forced changes in combat posture by these divisions well below that casualty threshold.

The next breakpoints study occurred in 1988.[5] There was absolutely nothing of any significance (meaning providing any form of quantitative measurement) in the intervening thirty-five years, yet there were dozens of models in use that offered a breakpoint methodology. The 1988 study was inconclusive, and since then nothing further has been done.[6]

This seemingly extreme case is a fairly typical example. A specific combat phenomenon was studied only twice in the last fifty years, both times with inconclusive results, yet this phenomenon is incorporated in most combat models. Sadly, similar examples can be pulled for virtually each and every phenomena of combat being modeled. This failure to adequately examine basic combat phenomena is a problem independent of actual combat modeling methodology.


[1] Dorothy K. Clark, Casualties as a Measure of the Loss of Combat Effectiveness of an Infantry Battalion (Operations Research Office, Johns Hopkins University, 1954).

 [2] Ibid, page 34.

[3] Headquarters, Department of the Army, FM 105-5 Maneuver Control (Washington, D.C., December, 1967), pages 128-133.

[4] The two exceptions included the U.S. 106th Infantry Division in December 1944, which incidentally continued fighting in the days after suffering more than 40 percent losses, and the Philippine Division upon its surrender in Bataan on 9 April 1942 suffered 100% losses in one day in addition to very heavy losses in the days leading up to its surrender.

[5] This was HERO Report number 117, Forced Changes of Combat Posture (Breakpoints) (Historical Evaluation and Research Organization, Fairfax, VA., 1988). The intervening years between 1954 and 1988 were not entirely quiet. See HERO Report number 112, Defeat Criteria Seminar, Seminar Papers on the Evaluation of the Criteria for Defeat in Battle (Historical Evaluation and Research Organization, Fairfax, VA., 12 June 1987) and the significant article by Robert McQuie, “Battle Outcomes: Casualty Rates as a Measure of Defeat” in Army, issue 37 (November 1987). Some of the results of the 1988 study was summarized in the book by Trevor N. Dupuy, Understanding Defeat: How to Recover from Loss in Battle to Gain Victory in War (Paragon House Publishers, New York, 1990).

 [6] The 1988 study was the basis for Trevor Dupuy’s book: Col. T. N. Dupuy, Understanding Defeat: How to Recover From Loss in Battle to Gain Victory in War (Paragon House Publishers, New York, 1990).

Also see:

Battle Outcomes: Casualty Rates As a Measure of Defeat

[NOTE: Post updated to include link to Dorothy Clark’s original breakpoints study.]

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Christopher A. Lawrence
Christopher A. Lawrence

Christopher A. Lawrence is a professional historian and military analyst. He is the Executive Director and President of The Dupuy Institute, an organization dedicated to scholarly research and objective analysis of historical data related to armed conflict and the resolution of armed conflict. The Dupuy Institute provides independent, historically-based analyses of lessons learned from modern military experience.
Mr. Lawrence was the program manager for the Ardennes Campaign Simulation Data Base, the Kursk Data Base, the Modern Insurgency Spread Sheets and for a number of other smaller combat data bases. He has participated in casualty estimation studies (including estimates for Bosnia and Iraq) and studies of air campaign modeling, enemy prisoner of war capture rates, medium weight armor, urban warfare, situational awareness, counterinsurgency and other subjects for the U.S. Army, the Defense Department, the Joint Staff and the U.S. Air Force. He has also directed a number of studies related to the military impact of banning antipersonnel mines for the Joint Staff, Los Alamos National Laboratories and the Vietnam Veterans of American Foundation.
His published works include papers and monographs for the Congressional Office of Technology Assessment and the Vietnam Veterans of American Foundation, in addition to over 40 articles written for limited-distribution newsletters and over 60 analytical reports prepared for the Defense Department. He is the author of Kursk: The Battle of Prokhorovka (Aberdeen Books, Sheridan, CO., 2015), America’s Modern Wars: Understanding Iraq, Afghanistan and Vietnam (Casemate Publishers, Philadelphia & Oxford, 2015), War by Numbers: Understanding Conventional Combat (Potomac Books, Lincoln, NE., 2017) , The Battle of Prokhorovka (Stackpole Books, Guilford, CT., 2019), The Battle for Kyiv (Frontline Books, Yorkshire, UK, 2023), Aces at Kursk (Air World, Yorkshire, UK, 2024), Hunting Falcon: The Story of WWI German Ace Hans-Joachim Buddecke (Air World, Yorkshire, UK, 2024) and The Siege of Mariupol (Frontline Books, Yorkshire, UK, 2024).
Mr. Lawrence lives in northern Virginia, near Washington, D.C., with his wife and son.

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  1. That is what was explored in the 1988 Breakpoints study. They ended up creating a laundry list of over 30 factors, then boiled it down to the most prominent dozen or so, and then created a flow chart based upon that. They were expecting a follow-on contract to then further test and develop their work, and this follow-on contract never arrived. So, the subject was explored, but nothing was definitively answered.

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