If I wanted to be a soldier, I would join an army. Otherwise it is quite illegal to go around shooting people, no matter how justified you are. Of course there are practical problems for frum Jews – Shabbos, kashrus, whether specific acts violate halacha since its very clear that the “superior orders” defense doesn’t apply under Torah law since HaShem is always superior to your comanding officer, and issues about whether an individual soldier is responsible for averios done by other soldiers just because he’s part of the army (if an army lets you be frum, but coerces other soldiers to do things contrary to halacha, are you guilty as an accomplice).
If I wanted to learn Torah full time, I’ld join a kollel. The problem is that kollels (unlike armies) pay poorly and I wish to be middle class. While I know that learning Torah is the ikar for our survival, but being a bit hasidische I’ld say there’s room for a baal ha-bayis now and them.