The existential threat of Amalek.
"A democracy must often fight with one hand tied behind its back."
Jewish law on the proper treatment of prisoners of war
Few traditional sources discuss the ethics of fighting noncombatants, but some Jewish laws of war do display a moral genesis.
When lives are at stake, Judaism permits--and probably requires--fighting.
Judaism distinguishes between commanded wars and permitted wars.
Combat and Conflict in Jewish Tradition. Jewish Views on War and Peace. Jewish Ideas and Beliefs.