It is basically a reminder that war requires serious consideration and it not necessarily a completely political matter but also a moral one.
Anyway, here are some criteria that were listed to determine if a war is just or not.
- The cause must be just. For instance, to protect people from unjust attack.
- It must be declared by competent authorities.
- It must be a LAST resort AFTER all possible peaceful solutions have been exhausted.
- Its ends must be proportionate to its means. The evils of it cannot outweigh the good.
- Its intentions must be right. It cannot be motivated by revenge or hate.
- Success must be probable. If there is no possibility of winning or if too many will be killed as a result of it, it is not just.