Casualties

So we are reading our fictional accounts of apocalypsse-in-progress battle, and the good guys are just mowing down the bad guys.  If it is one of the traditional penultimate battle scenes being fought at the defended berm, wall, etcetera thousands of attackers are wiped out by a handful of defenders.

Well obviously if you set up an artificial situation the results are going to get a little odd.

But what exactly does happen when an attack goes in.  Particularly what happens when you take out all the artillery, tanks, mortars, and other heavy weapons.

Expected attacker casualties

from Stress of Battle, David Rowland (The Stationary Office, 2007) via Salt (see below for link).


* 1 to 1 attacker/defender ratio; losses per defender: .25; losses per machine gun: 2.25
* 3 to 1 attacker/defender ratio; losses per defender: .5; losses per machine gun: 4.5
* 10 to 1 attacker ratio; losses per defender: 1.0; losses per machine gun: 9.0

Note that although the chance of success increases with the number of troops attacking, the number of people killed goes up as the number of targets become plentiful.  I am taking the machine guns to be light machines used as point defence weapons.  Not the heavy machine guns we discussed earlier.

The amount of ammunition fired to accomplish any casualties will be fairly large. 

Five Minutes of rooty-toot
John D. Salt, The Nugget, February 2008

If we were to assume that defending sections fired off 75 rounds per personal weapon and 750 rounds per machine gun (both figures in the mid-range of ammo loads...), the hitting rate would be something of the order of 300 rounds per hit at a 1:1 attack ratio, 150 rounds per hit at a 3:1 attack ratio, and 75 per hit at 10:1 attack ratio.  Given that most infantry fire is conducted below 300 meter, this standard of shooting is about two orders of magnitude worse than one might expect on the range.  Recall, too, that this is for defenders shooting at attackers, who are obliged to make targets of themselves in order to close [with] the enemy.

Shooting at prone or dug-in defenders would presumably be less effective still; in his book Passing it on (Bhavana, 200) about North West Frontier fighting, Sir Andrew Skeen says that "it is next to impossible to inflict loss on men behind cover with direct rifle fire", I would go so far as to say that not only is suppression the main effect of bullet fire, but it is, to a close approximation, the only effect.  It helps to explain why rates of expenditure are low in protracted close combat if people are not firing  because they are, most of the time, suppressed.  Reliable quantitative data on the suppressive effect of fire are, unfortunately, rarer than hen's teeth.

 So, what this means is that if we have 300 men advancing, in a modern (dispersed) fashion, 300 meters against 100 men firing from foxholes, or some sort of cover, the attacker will take 50 casualties and the defenders will have fired around 22,500 rounds (or about 608 pounds of ammo at 37 pounds per round for .223/5.56x45 NATO).   The defenders might loss one of their number.

On their way to having 1 in 6 of their numbers casualties will likely peak at around 100 meters.  At that point the defending troops start getting a little nervous and their aim/resolve begins to deteriorate.  It is in this zone, the last 100 meters that the attack will either succeed or fail.  It is not an accident that Poole called his popular (but at times rare) explanatory manual for NCO (Non-commissioned officers) The Last 100 Yards.  If the attackers loose their nerve, they will go to ground, and an extended ineffectual fire fight is likely to ensue.

So what makes the difference.

Speight and Roland, using historical norms for British troops, modeled soldiers level of war fighting resolve in the attack in a tiered fashion:


L.R. Speight and D. Roland in Modelling the Rural Infantry Battle: The Effects of Live Combat  on Military Skills and Behavior During the Approach Phase, Military Operations Research, V13, N4 2008.

Type A, roughly 7%of the force, avoid combat and are described as non-participating (NPA)

Type B, again 7% of the force, freeze at contact (FAC)

Type C, 36% , continue after contact, but subsequently halt and do not fire, the freeze during advance (FDA)

Type D, 37%, maintain their advance to the end, but make no effective use of their weapons, they are passive followers (PAF)

Type E, 11% are full participants in combat, but weapon use is sub-optimal, they are active followers (ACF)

Type F, 2% are the heroic performers - fully participating and making full effective use of their weapons, they are the heroes (HRO).

Note in a well run army, that has seen a little combat, the heroes will tend to be the experienced NCOs and officers.  They will lead their men into battle.  Some of their men will follow. As an aside, it can be seen why armies that do not have effective low-level leadership are so completely outfought by armies that make a religion of it.  If the troops come from a hierarchical background (they need to orders to act) they will sit on their hands if their is no heroes in command positions.  It also explains the odd battle field results of American troops in both World Wars where singular individuals would often run around and shoot up an enormous number of (usually) Germans.  The Americans, excepting the Marine Corp which saw a lot of action in Latin America, had not had enough time to sort out its small unit leadership situation.  They were often pretty raw.  Almost religiously non-hierarchical Americans not feeling compelled to wait for orders, and maybe not always listening to them anyway , none-the-less derived a lot of their effectiveness from these singular (crazed?) heroes.  American "heroes" didn't wait for orders.

Without going into to many details, Speight and Roland note that while the ability to actually hit a target goes way down, that the target area to suppress the target (get him to hit the deck) is much larger.  They need to hear the bullets.   The net effect is that small arms do not cause many casualties, they do make people hit the deck. 

Better quality (elite) troops will inflict more casualties on the attackers.  Mostly because they will have more defenders willing to stick their heads up and shoot at any exposed attackers.  The suppressive effect of this additional firepower negates the risk of sticking your head up.  The elite troops will not suffer greater casualties.  Raw conscripts tend not to stick their head up when being under effective suppressive fire.  This tends to magnify their disadvantage against elite troops who are putting out more firepower.  In the case of the study, elite troops such as the Ghurkas were 160% effective versus the normative benchmark at both inflicting causalities and the number of heroes (based on gallantry medals).  As an aside, machine gun crews, tend to be less susceptible to suppression.  My guess is it is because they view their significant firepower as being directly effective in their units survival.  Working as a team, the crew also appears (based on this study) to follow the lead of the bravest person present.

One final important note that the authors make, is that a lot of small cumulative advantages will add up to very non-linear results.  The various 10 to 60% advantages of the elite units, and their (usually) elite leadership, can add up to a force effectiveness 10 to 20 times their opponents.  This does not make them supermen.  The catastrophic levels of damage that modern weapons can inflict insures that elite troops will over time be worn down.  Elite troops used too frequently over too long of a period of time, tend to lose their edge.

The other interesting item, not specifically stated but implied, is that it is very likely that the majority of the kills-major injuries are inflicted by the "heroes" and machine gunners.  Since heroes performance is not degraded by fear, they actually make the easy shots.  If they see the target at 100 meters, they are likely to hit it.   The numbers indicate that, outside of the machine guns, 90% of your kills/injuries from small arms are inflicted by 5% or less of the troops.  This would make infantry combat rather  similar to aces in aerial warfare. Before I had started looking at the numbers, that would have surprised me.