The oldest soldier in my platoon in Bosnia was 32. We called him “grandpa”.

He was quite fit (he didn’t drink alcohol or smoked) but there were only a few situations where we had to go near our physical limits.

During the Kosovo War, our oldest soldier was 28. This war was much more physically demanding. We were on the move practically all the time, night and day.

Our longest battle in Kosovo lasted 24 days while in Bosnia, we never fought longer than four or five days.

Several answers in this threat assume that war means staying in a FOB and doing patrols from time to time. For this kind of activity, a soldier can indeed be much older, forty, or even more.

However, when it comes to guerrilla and small unit warfare in a conflict that lasts for months or even years, you’ll feel every bone in your body when you’re over thirty.

The older you are, the more time you need to recover, something which is impossible in a high-intensity conflict. You may last for a couple of weeks but not longer.

You’re simply too old.