Well, you see, if men stay alive, but women are killed, society collapses eventually as not enough new people are born. It sucks being a man in this scenario, but it is what it is.

Arguably, not enough people are being born as it stands. We're already in your collapse scenario.

I suspect one tool governments across the world will resort to when they get desperate about sub-replacement fertility is changing mandatory conscription from males to the childless. Quite strong incentive, not be sent to the meatgrinder.

And if you include women (well, all genders) directly in the war efforts you double the amount of soldiers you have, which would increase your chance of winning and not needing to repopulate.

You can lose a war, yet still keep your country. You can also win a war, yet still need to repopulate.

If you refuse to fight, you lose.

If you all agree to refuse to fight, you win.

https://en.wikipedia.org/wiki/Prisoner%27s_dilemma

The key here is to refuse fighting. Nobody becomes a hero by becoming a murderer whose goal is to defend the political power of Stalin, Napoleon, Bush, or whoever.

Someone has to stay behind and make ammunition.