" Individuals in the middle ages were considered to have already received grace through baptism and their continuing participation in the sacraments.4 One early implication of this interpretation is that love is put aside once jus ad bellum criteria have been met. Killing the aggressor is no longer the act of loving punishment, but rather a necessary evil in order to satisfy a greater good. This is one explanation of why Aquinas was apparently uninterested in jus in bello considerations; the actual killing exists outside of the realm of Christian conduct.5 Jus in bello criteria come later. It is this balancing of good and evil actions that lead to the questions of proportionality and double effect. In contrast, proportionality, double effect, and jus in bello criteria never need be raised in Augustinian thought; as long as the killing is personally done with charity in the heart, it is justified. Caritas is so important in Augustine's thinking that it justifies wars to convert non-Christians. This is the ultimate act of love in this argument: repairing a flawed relationship between the conquered and God.6.
Now that we have established the origins of the theory, we must define what is meant by war. It is "defined as a state of conflict between two or more sovereign nations carried on by force of arms."5 Looking into this definition more closely we see that war involves a state of conflict contrasted with passing conflicts such as border skirmishes or momentary conflicts. It involves sovereign nations, which rules out civil wars and riots. Also a nation fights a nation and not a particular individual or group in a nation. Force of arms excludes for example trade embargoes and blockades. These make up the basic components of a war. .
A great impetus to the Just War Theory was St. Thomas Aquinas. He emphasized St. Augustine's statements about war and added a little to them. He followed a similar reasoning breaking up his argument into three necessary conditions for a just war: authorized authority, just cause and rightful intention.
