Jus Ad Bellum

At the Nuremberg trials, during a discussion of Just War Doctrine, a point was reached where they needed to distinguish between just reasons to go to war, and just specifications of how war should be fought. Jus Ad Bellum is "when it is right to go to war". How war should be fought is Jus in Bello.

One of the most comprehensive descriptions of Jus Ad Bellum came from Catholic bishops in America in 1983.

Conditions to be met for Jus Ad Bellum -

1. There must be a just cause. They said 'War is permissable only to confront a real and certain danger'.
2. War must be declared by proper authority.
3. Comparative justice - the justice of the claims of both sides must be compared.
4. There must be a right intention in going to war.
5. War must be a last resort.
6. There must be a reasonable probability of success.
7. There must be a proportionate comparison between the injustice suffered and the suffering caused by the war. It's not just to nuke a city over a fishing dispute.