@madel,
When is military action justified? This is a really loaded question. As such, it will be very hard to argue for your point. I have found that if you simply argue the reasons for war and during war (jus ad bello
and jus ad bellum), you kinda dig yourself into a very deep hole because there has never been any real consensus to the issue. So though you can argue with them, you have to be careful.
So, what to do for your paper? If you were to take this topic (i.e. when is military action justified), you can simply address several good texts on the subject and support your general thesis? which is whatever slant you interpret from the texts of your choice.
This is the way I would approach it
First, I would address an article by
Hannah Arendt called "Power and Violence." I remember reading it in University, it is very good. It's complex, but you can twist the articles conclusion in a number of ways. It breaks down the issue into abstract terms so that you have a good deal of latitude with them. Once you develop an abstract thesis, like how you are for or against military justification for example, you can give supplemental material to support that thesis.
If you remember,
George Bush gave an address to the nation on September the 11th. I'm sure you can find a transcript online of the speech. In it, he outlines the justifications for war. It is at this point that you can introduce the essential element of Jus ad bello and jus ad bellum. DO NOT OVERLOOK THESE NOTIONS. These are PRIME ideas in political philosophy, and you will get flak for not addressing them. Then, for the bulk and conclusion of your paper, I would suggest
Richard Falk's "Defining a Just War." That should give you more than enough things to talk about for the rest of your paper.
Just make sure to link the relevancy of Ardents "power and violence" to your thesis? whatever that may be. Then support that thesis with a) George Bush's address, which would link to b) Falks "Defining a just war."
If you need more elaboration or more sources, I'm more than happy to help out. Chances are most of these articles are on JSTOR.