Aye. Soldier being out on a combat field for months are going to jack off quite a few times to all sorts of things...
Whilst that wouldn't actually fit to a "currently ongoing combat/action" (as in when guns n explosions, n blood/gore, are already lighting up the view) that is something that would happen at some moments before n after such combat scenarios. I think the TV series "Generation Kill" mentioned a term called "combat jack" or something :D