You need to know abut the principles of a Just war anddifferent types of pacifism.
You also need to be aware of where the different ethical theories stand in relation to these issues.
In the Just War theory you should become familiar with the rules for (i) going to war (ii)behaviour during the was and (iii) what happens when a was has ended. These three are known as Jus ad Bellum, Jus in Bello and Jus post Bellum.
JUS AD BELLUM – JUS IN BELLO – JUS POST BELLUM
Then there is the alternative to a Just War Theory with Realism and Christian Realism
Pacifism
Finally you need to look at the other side of the coin with different types of pacifism. Those people who oppose war, at all costs, those who oppose it on religious grounds and those who oppose war when they feel there is an alternative to it.
