A legitimate authority must declare the war. The war should be defensive, not aggressive. All peaceful means, including good-faith diplomacy, need to be exhausted first. Finally, moderation and differentiation require focusing the war on the aggressors, not innocent civilians. It is presumed that all sane people prefer peace, never want to initiate war, and accept even the most justifiable defensive war only as a sad necessity.
Today there is no shortage of just causes to fight for.
Pacifists urge the Church to be a voice of nonviolence for life and creation. If we do not emphasize the law of love, we betray our trust, our vocation. Today many pacifists reject even noncombatant positions such as chaplain or medic, as well as any work that directly or indirectly assists military operations. Many also engage in nonviolent protest at military bases and industrial facilities producing nuclear weapons and other armaments. Some refuse to vote for political candidates or pay taxes that fund the development and sale of weapons and foment war.