What was the average age of tank crews, in particular commanders, in WW2?

Tank commander was a matter of rank, not age. The typical US Army enlisted tank commander, and I am only addressing the US Army in this missive, was a sergeant, with eleven of them commanding tanks out of eighteen tanks in the average medium tank company. Three tanks assigned to the company HQ and five to each of three platoons. At the company HQ, one tank was commanded by the company commander (rank- Captain) and the other two were commanded by sergeants. The typical platoon had one tank commanded by the platoon leader (rank – 2d lieutenant), one commanded by the platoon sergeant (rank – staff sergeant), and the remaining three by sergeants. See here.

A company commander could be as old as 30, but that would be a little unusual with the rapid expansion experienced by the Army and even more so as the effect of casualties caused younger officers to be moved into higher positions. As an aside, I know of one army officer who was a 2d lieutenant platoon commander in June 1940, a captain, company commander in 1943, and in his regiment’s tour of the European countryside from June 1944 to May 1945, still a captain when they came ashore, was moved up to the battalion S-3 slot, was promoted to major, became the battalion XO, then to battalion CO and was promoted to lieutenant colonel as the smoke cleared away. He was 27, two months shy of 28. His brother, three years younger, and an Air Corps fighter pilot, a 2d lieutenant of cavalry in May 1942, by the end of 1944 he was a major and a squadron commander. His promotion to lieutenant colonel come through on the day he was shot down and killed in early January 1945; he had turned 24 the previous November. Promotions came fast in places of combat.

Indeed, one could enlist or be inducted, go through basic training, advanced training, work ones’ way through the various crew positions in a given armor unit, and, with promotions coming at a rate of one every six months, a not at all unusual rate, starting at 18 one could be a sergeant by 20 and commanding one’s own tank.

Generally, in the tank business, presuming one even wants to move up in the hierarchy (and certainly there were those who were perfectly content where they were, there were soldiers, even in armor units in combat, who were privates for the duration), one starts as a driver, moves to loader/bow gunner, to gunner and thence to tank commander. As the war goes on, the replacements became incrementally younger, thus younger in each position. Remembering that age really has nothing to do with equation, it becomes a matter of what was allowable by regulation. That matter is fairly simple. If one occupied a position calling for the next highest rank for 60 days, presuming ones’ performance in that position is satisfactory, then the commander with the authority to do so, say a regimental commander, when speaking of enlisted men, could sign-off on a promotion. So, a driver, presuming his TC is amenable, could move up to loader/bow gunner, slot and be promoted tor PFC; if he becomes a gunner, then at some point, a corporal. And if a unit commander finds himself with a tank in need a commander, he starts looking real hard at his available gunners and finding one he thinks might make a good TC, that fellow gets the tank and probably a promotion to sergeant . . . which means, of course, that now there is a tank in need of a gunner, and so on. Unit commanders had a lot of flexibility on who was assigned where and those assignments largely determined one’s rank. So, the younger the replacement, the younger in each position, including the TC.

And it was nasty, from the 1946 Infantry Conference on Personnel Policies and Procedures this passage:

’All replacements were received and absorbed during combat. Infantry and armored replacements were deplorably unsatisfactory. Few infantrymen knew extended order formations, scouting and patrolling or their crew-served weapons. Out of 26 replacements for the tank company, only one man had ever driven a tank. Many were needlessly lost.’
-- Col -C. E. Steele, CO, 141st RCT, 36th Inf Div, 7 October 1944, Vosoges, France.”

I am sure he is addressing both infantry and tank losses and probably leaning more towards the infantry side of the equation, but if a tank driver is killed in an M-4, there is a better than even chance that so was most if not all of the crew. That would mean a need for a new tank and the least a new TC and gunner drawn from what experienced crews were still available. A continuous domino effect.

Certainly, one can easily find the average 26 years old statistic anywhere you look. The Saturday Evening Post even goes on to describe him in detail.

But this statistic does not necessarily take into account the “teeth to tail’ factor. In the ETO, amongst combat divisions, the ratio of combat to support averaged about 1 to 1.6 – only about 38.5 percent were front line combat types. See here and here.

Armor units require greater “tail” than infantry for obvious reasons. And the more technical the support, the more one would tend to find, compared to those on the front line, relatively older soldiers

Realistically, one would expect a sergeant, a TC, probably not older than 24, to be leading around a crew of 19 to 22-year olds; combat, as they say, is a young man’s game. Senior NCO types came from the ranks of those who had survived so you see most TCs topping out at sergeant – the rank specified in the TO&E while a small minority moved up to platoon sergeant and upwards . . . they, too, needed to be replaced when the time came.

As to whether or not there is an actual statistical study revealing the ages or average of TCs in WW2 . . . I’d suggest that it would be a very specific study in which the US Army would have had little interest or time to devote.