Some volunteers who signed up at the beginning of the war with Russia are mentally and physically exhausted, and there is a lack of younger fighters to replace them
I guess that means there's a huge pool of younger Ukrainians still to pull from for the military? I'm guessing that's a good thing for their long term recruiting prospects.
It's the opposite. The pool of young people to pull from is smaller everyday.
In this regard, Russia has the advantage where they can just keep throwing more and more bodies into the war without major unrest. Luckily Wagner is gone, as they had the human wave then special forces combo down to a science, but the problem of Russia having exponentially more manpower at their disposal remains unless they begin drafting all Women between ages 18 - 60. Which will likely never happen.
I don’t agree that this is necessarily a weakness or that it’s overly strange.
While they might not be able to quite hit the peak fitness of someone in their 20’s and 30’s, you also gain a large amount of meaningful mental fortitude as you get older.
In short you have seen more shit and dealt with more shit. So generally you can bear more headship and pain before breaking, also probably less prone to discipline issues, and the older ones likely provide a good example to the rest.
In a war for the survival of your nation all able bodied people are needed. There are naturally more older people than there are younger ones.