Human Factors In Warfare: Defensive Posture

U.S. Army troops shelter in defensive trenches at the Battle of Anzio, Italy, 1944. [U.S. Army Center for Military History]

Like dispersion on the battlefield, Trevor Dupuy believed that fighting on the defensive derived from the effects of the human element in combat.

When men believe that their chances of survival in a combat situation become less than some value (which is probably quantifiable, and is unquestionably related to a strength ratio or a power ratio), they cannot and will not advance. They take cover so as to obtain some protection, and by so doing they redress the strength or power imbalance. A force with strength y (a strength less than opponent’s strength x) has its strength multiplied by the effect of defensive posture (let’s give it the symbol p) to a greater power value, so that power py approaches, equals, or exceeds x, the unenhanced power value of the force with the greater strength x. It was because of this that [Carl von] Clausewitz–who considered that battle outcome was the result of a mathematical equation[1]–wrote that “defense is a stronger form of fighting than attack.”[2] There is no question that he considered that defensive posture was a combat multiplier in this equation. It is obvious that the phenomenon of the strengthening effect of defensive posture is a combination of physical and human factors.

Dupuy elaborated on his understanding of Clausewitz’s comparison of the impact of the defensive and offensive posture in combat in his book Understanding War.

The statement [that the defensive is the stronger form of combat] implies a comparison of relative strength. It is essentially scalar and thus ultimately quantitative. Clausewitz did not attempt to define the scale of his comparison. However, by following his conceptual approach it is possible to establish quantities for this comparison. Depending upon the extent to which the defender has had the time and capability to prepare for defensive combat, and depending also upon such considerations as the nature of the terrain which he is able to utilize for defense, my research tells me that the comparative strength of defense to offense can range from a factor with a minimum value of about 1.3 to maximum value of more than 3.0.[3]


[1] Dupuy believed Clausewitz articulated a fundamental law for combat theory, which Dupuy termed the “Law of Numbers.” One should bear in mind this concept of a theory of combat is something different than a fundamental law of war or warfare. Dupuy’s interpretation of Clausewitz’s work can be found in Understanding War: History and Theory of Combat (New York: Paragon House, 1987), 21-30.

[2] Carl von Clausewitz, On War, translation by Colonel James John Graham (London: N. Trübner, 1873), Book One, Chapter One, Section 17

[3] Dupuy, Understanding War, 26.

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Shawn Woodford
Shawn Woodford

Shawn Robert Woodford, Ph.D., is a military historian with nearly two decades of research, writing, and analytical experience on operations, strategy, and national security policy. His work has focused on special operations, unconventional and paramilitary warfare, counterinsurgency, counterterrorism, naval history, quantitative historical analysis, nineteenth and twentieth century military history, and the history of nuclear weapon development. He has a strong research interest in the relationship between politics and strategy in warfare and the epistemology of wargaming and combat modeling.

All views expressed here are his and do not reflect those of any other private or public organization or entity.

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  1. There was some criticism regarding defensive posture, namely that “it is not always beneficial for a defender to adopt such a posture, if the enemy is far more proficient in maneuvering and far superior in firepower” (something like, “sitting ducks under superior firepower”, which is a bit controversial since it allows your forces to survive longer).

    In my models I included the conjecture that all combatans are going to “carry over” their proficiency towards everything they are going to do, i.e. their general efficiency will translate into attacking as well as defending. The interesting part here is that it usually resulted in a range of 1.396 to 2.5 (sometimes below).
    One example I could give is the classic Lanchester equation (yes I know, most people do not accept Lanchester), which gives a value of 2.46-2.5 for the Battle of Kursk (Zitadelle, defensive phase) for the German Army, yet adjusted for defensive posture you will land pretty close to Dupuy’s figure of 2.68.

    I also have not found any model that would cope with “combat pace” to adjust to casualty fluctuations (and thus jumps in potential), which is a problem for longterm estimations.

    • Dupuy concurred with Clausewitz’s assertion that while the defensive was the stronger form of combat, taking the offensive was required for success in warfare. It is also possible to combine strategic and operational offensives with defensive tactics to take advantage of the power of the defensive posture.

      Given enough data, it is likely possible to tease out specific trends, such as particular armies, units, or leaders being more proficient in the attack or on the defensive. Dupuy did note that there were differences in the combat effectiveness of specific divisions in World War II. It should also be possible to identify how factors such as casualties or exhaustion affect combat effectiveness over time. Again, the only real limitation is the availability of the data.

      • Ultimately, what drives us into a different posture is mentality, psychological factors due to the current situation the participants are going to find themselves in (taking the Kursk example: Facing the unkown, while relying on previous experiences (the Summer offensives of 41 and 42), as the battle only happened because the Soviets decided to stand idle after the 3rd Kharkov.
        The unkown variable was the German forces strength (while on the other hand, the Germans were unaware of the Soviet reserves).
        I guess one could argue that the decisive factor for succeeding are force ratios, efficiency is going to dictate how well the combatant is going to fare while defending or penetrating (in this case the defenders losses were higher but there is no doubt that the first day’s initial attack was a difficult task for the Wehrmacht as losses were fairly close, only thereafter did fluctuations occur, as the defensive line was hardly “defensive” anymore, that is where reserves had to save the day, when specifically speaking about the southern flank).

        If we observe operation Desert Storm, Iraqi forces just prolonged the inevitable. Forces are going to shift and go over to the attack if they think there is a chance of winning – either that or they are simply attacking out of desperation (e.g. IJN forces in the pacific, “reclaiming honor”).

        Napoleon always preferred to stay on the attack and to never give up the initiative, seeing defense merely as a form or tool for a possible counterattack (even in battles such as Aboukir, Jena and Auerstedt).

        • I would agree that assuming a defensive posture is a prudent response to the unknown or ambiguity, particularly given the dire consequences of being surprised or outmaneuvered on the battlefield. I also agree that for Napoleon, defense was a means to regain initiative and attack. One of Dupuy’s timeless verities of combat is that the defensive posture is necessary when successful offense is impossible. Another is that initiative permits the application of preponderant combat power. Successful commanders employ the defensive, economy of force, and initiative to mass combat power to facilitate offensive action at critical points on the battlefield.

  2. The start of the first quote seems to be saying that humans tend to shift to defensive postures when they feel sufficiently threatened. Then it shifts to pretty much saying that this is a good move because being on the defensive is a force multiplier. Both things can be true but it’s not clear that the first one implies the second.

    As Stiltzkin points out, our instincts could drive us in the wrong defensive. That is, we realize we’re in trouble, get defensive but that actually makes things worse.

    There might be an evolutionary argument running from the second to the first. That is, if being on the defensive generally IS a force multiplier then humans who get defensive under pressure will have higher survival rates than those who attack under pressure so our brains get wired for defense. This is a cute idea but I kind of doubt it because it presumes that reacting defensively has been the right thing to do for a really long time to the point where are brains have become hard wired for this behaviour.

    I don’t really have a conclusion….just thinking out loud….

    • Mike, this is a fair observation. My feeling is that Dupuy’s assertion about defense makes more sense in the broader context of fear being the primary human factor on the battlefield. Whether or not humans are naturally inherently aggressive, it has been the case since the beginning of recorded warfare that soldiers require motivation through leadership and moral inspiration to fight effectively. Fighting, whether on that attack or in the defense, requires a conscious choice, I think, to overcome one’s inherent fear.

      This ties into another aspect of human behavior on the battlefield, namely involuntary changes in combat posture or unit “breakpoints.” Why do units stop attacking? Why do they stop defending and start retreating? Sometimes it is by the order of leadership, but it also happens spontaneously. Do this occur when individual soldiers decide that continuation of the present course of action will end in failure or defeat? Are they reacting out of fear or reason? Both, perhaps?

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