War

Just War Theory: The following are the conditions set down by the Catechism (#2309) supporting a war as just:

—the damage inflicted by the aggressor on the nation or community of nations must be lasting, grave, and certain;

—all other means of putting an end to it must have been shown to be impractical or ineffective;

—there must be serious prospects of success;

—the use of arms must not produce evils and disorders graver than the evil to be eliminated. The power of modern means of destruction weighs very heavily in evaluating this condition.

Basically, going to war is only permitted when it is necessary to protect the nation from serious and continuous harm from an unjust aggressor, everything else has been tried to bring peace, war appears to be a legitimate way of ending the unjust aggression, and the end result is judged to be better than the current situation. These conditions must all be met before the commander-in-chief of any nation declares war.