“Let us not forget this: War is in itself a crime against humanity. People need peace! The world needs peace!”
There are such things as just wars if the objective is to stop evil, such as during World War 2. If evil is allowed to proliferate, it causes untold suffering, misery, and death. The only way to stop evil is by force. That's true even at the micro level when combating crime on the streets. Turning the other cheek is a good practice when it comes to interpersonal relations but it does not apply to nations. And it certainly doesn't infer that someone should allow themselves to be harmed. God put survival instincts into every living creature for a reason. I don't believe God will condemn anyone for defending themselves with lethal force if need be, as there is a clear distinction between murder and killing.
We should model our lives after Christ, but people forget there are two facets to his character. The first time he came as a lamb to be sacrificed. Even then he showed he wasn't a pacifist when he turned over the tables of the money changers and drove them out with a whip. But the second time, he's coming as a lion to make war (Rev 19:11) and forcibly remove the anti-Christ and those allied with him. He's not making war alone either; he's coming back with the armies of heaven (Rev 19:14). So, yes, even in the heavenlies there are armies and war. One day we will beat our swords into plowshares, but that day is not today. Even Ecclesiastes 3:8 affirms there is a time for war and a time for peace.