What are the two principles to the jus in bello part of the just war theory?

The purpose of the doctrine is to ensure war is morally justifiable through a series of criteria, all of which must be met for a war to be considered just. The criteria are split into two groups: "right to go to war" (jus ad bellum) and "right conduct in war" (jus in bello).

Transcontinental railroad was the most effective way to travel.