What is a reasonable officer casualty rate in a combat action?

Question

Define senior officer casualty percent (henceforth referred to as SOCP) as $\frac{C_{off}}{C_{total}}$ where $C_{off}$ is the count of officer casualties above the captain rank (for reference, captains usually command about 80-150 troops) and $C_{total}$ as the total casualties taken by a fighting force.

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In my novel, the opposing army launches the April Offensive, where a brigade-size (1,000–5,500 troops) surprise attack the forces guarding a mountain pass. Preliminary artillery bombardment weakens their defenses, but the officers are able to marshal the troops together and repel the enemy forces. Unfortunately, although the guard unit took relatively medium losses, many officers, including the commander are killed, so they retreat.

My question is, what is the highest "plausible" SOCP, where relatively many officers are killed while relatively few troops are killed? By this I don't mean "make them shell the officer's club", the troops are marshaled into their proper subdivisions when the attack occurs. Examples from history are encouraged.

Other notes that may be helpful:

1. Shelling begins at dawn, ~6:00 AM. Officers form ranks and prepare for the enemy landing. There are about 1,550 defenders.
2. Approximately 2,000 troops land at 6:15 AM on the left flank of the defenders, including 80 sniper teams.
3. A second wave of approximately 2,000 troops land at 6:45 AM on the right flank. At this point the commander is dead, and his second-in-command rallies the troops to contain the enemy.
4. Fighting finishes at ~11:00 AM, with the enemy repulsed, the defenders take ~240 casualties (not bad considering their numerical inferiority)

In response to the questions raised:

Are you discussing casualties in attackers or defenders.

Defenders.

Also this sounds very WW1 to me, so could you indicate the tech level?

Approximately WW1, maybe a little after

In particular are senior officer uniforms significantly different from junior ranks (e.g. could a marksman spot one easily) ?

Senior uniforms are dark blue, while junior uniforms are cornflower blue, so yes.

In response to Odin's questions:

How easy it is to replace the said officers,

This is an aging military, senior officers with experience are especially hard to replace.

how aggressive they are leading their own troops, and the

In general, the platoon commanders are expected to do the fighting, while the company and up commanders being "senior" are expected to see the "big picture" and command their units

ideology of the militaristic forces involved.

This is undecided for me yet.

Answer 1

Say you have a brigade with three combat battalions, each with three combat companies. Nine company HQs, three battation HQs (with alternate and rear CP?), one brigade HQ (definitely with an alternate).

• Nine line company commanders.
• Three line battalion commanders with their staffs. Say the captain-and-above officers are the the commander, executive officer, operations officer, intelligence officer, and logistics officer. That's fifteen. Their assistants are lieutenants or senior sergeants and thus not in your SOCP.
• One brigade commander, also with those four staff positions. Say each has a captain-or-above assistant for the second CP.

That's 34 senior officers out of 5,000 troops, or a bit under 1%. Could be a few more, but I'll assume that chaplains, surgeons, and clerks-with-rank-tabs don't really count. The brigade took 5% total losses, so if they were randomly distributed one would expect two senior officers to die.

Are senior officers expected to take extra combat risks?

That depends on the culture of the service. A squad leader is expected to lead by example, a company commander might be expected to command the company, which usually doesn't mean getting bogged down in a little skirmish. On the other hand, senior officers may be expected to do a commander's reconnaissance and see with their own eyes what they're getting into.

Is the enemy targeting command posts?

Assume the CPs are well dug in, and if a shell hits the officer's mess that mess will be empty. Still, if each company or battalion CP gets the attention of some enemy mortars, you can justify a couple of senior officers being taken out.

Is the enemy targeting senior officers?

Imagine a dozen snipers on the enemy side who target radio operators and especially officers. If each of them gets one officer, that would be one third of the total calculated above. Have the defenders learned yet that one does not salute a senior officer in a combat zone?

Summary

You can justify relatively high or relatively low casualty rates, depending on how you want to spin the usual tactics. Give the enemy one sniper per platoon and officer casualties will go up sharply. Train the officers that a captain is supposed to command the entire company and not micromanage his lead platoon, and it will go down.

Answer 2

An interesting question, and as pointed out by others, there are so many variables which may impact the calculation, that it is difficult to model from scratch.

One option though, is to turn to history. It is our good fortune that the British War Office published detailed records of all manner of things for the First World War. Relevant for these purposes, this included all casualties by type by month for the Army in France. Should you wish to follow up, or learn more, the work is titled Statistics of the Military Effort of the British Empire During the Great War: 1914-1920.

In formulating this response, I have restricted the analysis to the ‘killed’ category, ignoring the ‘died of wounds’ and ‘died of disease’ ones in the process. I’ve also summed across the ‘Regular Army’, ‘Territorial Army’, ‘Canadian’, and ‘Indian Native’ bandings. Unfortunately, there is no detail on the ranks of the officers killed. However, the ratios of officer ranks indicated by another response here could be used to estimate that level of detail. Finally, since seasons are important (the most conspicuous day of European war history being 22 June), I’ve restricted the analysis to the month of April for each of the years. Doing so, I have found the following:

1915: 5.25% (288 officers and 5,197 other ranks)

1916: 4.43% (157 officers and 3,386 other ranks)

1917: 5.9% (1,424 officers and 22,700 other ranks)

1918: 6.58% (949 officers and 13,475 other ranks)

As an observation, there is little variance in the percentages, in spite of a steep increase in casualty totals for 1917-8. Also, although not displayed here, the ratios hold true for the individual banding, suggesting that the ratios may be a good indication of the OCP. If we bear in mind that the British Army in France for World War One effectively represented three ‘generations’ (the original, professional and experienced army – all but wiped out by 1916; Kitchener’s Pals Battalions – a tragic volunteer force; and the final conscripted army), then it is encouraging to observe that the ratio holds true in spite of levels of experience and professionalism.

Hope this helps.

Answer 3

Another answer from me. I'm assuming that you want to explain why the unit pulled back after the death of a plausible number of officers. Bringing the number of qualified commanders down to a mere handful means that random chance can justify a high percentage of casualties.

Who is qualified to command combat units?

Assume that the military laws and traditions of the defender have a strict division between line officers and staff officers. A line officer commands, a staff officer administrates and advises. For a historical precedent, look at the struggle of 19th and early 20th century Royal Navy engineering officers to get accepted as 'real' officers in the chain of command.

Something like this would be easily explained if the defending army had an aristocratic tradition, and if a glass ceiling kept all but the most conspiciously gallant commoners out of line commissions. Why, those sons of merchants are perfectly suited to become paper-pushers in uniform. Couldn't do without those splendid chaps. As long as they don't get ideas above their station.

To add insult to injury, count artillery officers as non-line specialists.

If you take only brigade, battalion, and company commanders into account, the available pool of combat leaders shrinks sharply.

Battalion, Brigade, Regiment?

Those are ancient terms whose meaning changed over time. If your story is set at WWI-era technology, it makes sense to think of infantry.

• A battalion are several infantry companies with a headquarters, some logistics (cooks and clerks), and some heavy weapon support. This could be an anti-tank platoon or company, a mortar platoon or company, a machine gun platoon or company, perhaps even light howitzers. Perhaps a few scouts as well.
• A battalion combat team is a battalion, perhaps with one infantry company swapped for an armored company, and with a higher number of logistics and support. Probably a company-sized artillery battery.
• A regiment are several infantry battalions, perhaps with a combat headquarters, perhaps with some logistics. Perhaps the heavy weapons from the battalion are concentrated here in companies/batteries instead of being parceled out to the battalions, but the totals remain the same. Or the regiment is only an administrative unit, and for combat the battalions are brigaded into brigades.
• A regimental combat team is a regiment-sized unit, which might have swapped one infantry battalion for an armored battalion, plus logistics and other support services -- an artillery battalion, an engineer company or battalion, perhaps even aviation.
• A brigade may be two or more regiments, or a regiment-sized unit with more support, much like a regimental combat team. The really big "division of brigades of regiments of battalions" was a reaction to the losses of WWI trench warfare.

An infantry battalion could be around 1,000 people, a brigade or a regimental combat team around 5,000.

Assume that your defenders are a large battalion combat team instead of a weak regiment or brigade. Four or five infantry companies, a machine gun company, a mountain howitzer battery, an anti-tank platoon, an engineer platoon, plus medics, cooks, and drivers/teamsters to keep them fed and supplied. That could be a 2,000-strong force which defeats two separate 2,000-strong attacks and gets mauled in the process.

This force would have one battalion commander and his headquarters and six or seven combat company leaders. Call it one lieutenant colonel, two majors, and ten captains. Only five or six of them are infantry commanders.

Answer 4

This question is so full of variables it is almost impossible to answer. Some issues would include the tech available: is the commander getting information via radio, via runners or should they go forward to see on their own? What is the actual doctrine being used? A flexible or elastic defence might see units withdraw under fire to allow the enemy to be sucked into artillery and machine-gun kill zones, while other forms of defence might involve rapid and vigorous counter attacks of enemy incursions, which would obviously expose leaders to more enemy fire. And of course, how important is this objective? Would a commander be willing to retreat to save his unit, or would he have to maintain the position at all costs to protect a vital point or key terrain?

Even particular circumstances can affect the battle. If the enemy achieved surprise, they might be able to catch the defending commanders as they are forward inspecting the position. If the assault is particularly successful, the defending commanders in the sector may have to leave the command post to go forward to see what is going on and understand the situation so they can prepare new orders.

The attacker's doctrine is also important. Do they deliberately set up situations with artillery, smoke and gas to blind commanders and lure them forward? Is the attacking forces doctrine to deliberately locate and target commanders, command posts and possible alternate positions? If they just mechanically smash positions with artillery, how much artillery is being used and how long is the bombardment and how deep is the zone being bombarded?

This is just a very loose handwave of some of the factors which would affect the question. Once you have understood the doctrines being used by the forces, the local and strategic situations and other factors like moral and logistical considerations (commanders might be going to the rear in order to collect reinforcements or demand additional artillery support and ammunition and other supplies if higher headquarters isn't available through normal means), then you will have a better understanding about the relative risk each commander is taking. Of course there is also a huge element of chance in warfare, a nearby shell might kill the signaller but leave the commander untouched, or other equally strange and unlikely occurrences (good or bad) could affect the survival of the commander.