The phenomenon of the sacred band.

[Montmorency]

the reason why the French paratroopers (and others) jumped on Dien Bien Phu

Many of them were soldiers going on reprieve, with no prior training in para-jumping. Yet hundreds of them volunteered to return to battle, to jump. The casualty rate was enormous in those drops...

[Papewaio]

I think the argument that men will do something foolish and/or heroic because the other person is a woman is more weighted towards a strawman argument than a valid one.

Men do foolish and heroic things for other men. The real issue would be if they only did it for one gender.

Also the mateship factor is one that is part of recruit training in the Australian army:
"To inculcate soldierly qualities including: a will to win, dedication to duty, honour, compassion and honesty, mateship and teamwork, loyalty, and physical and morale courage"