He said to them, “But now if you have a purse, take it, and also a bag; and if you don’t have a sword, sell your cloak and buy one. It is written: ‘And he was numbered with the transgressors’ ; and I tell you that this must be fulfilled in me. Yes, what is written about me is reaching its fulfillment.”

The disciples said, “See, Lord, here are two swords.”
“That is enough,” he replied.

Luke 22: 36-38

Recently RELEVANT Magazine published an article on the legitimacy of the Iraq War viewed from a Christian or Christianity-inspired perspective. RELEVANT interview two Christian experts on their respective subjects:

Daniel Heimbach from Southeastern Baptist Theological Seminary on JUST WAR, and

David Gushee from Mercer University on JUST PEACEMAKING.

I recommend the article because I believe both experts present good points on the legitimacy of military conflict and also at the application of military-exercise theories to contemporary events and conflicts. However, I would like to emphasize the last question that is asked on torture and aggressive interrogation since it is in those cases that these theories, and our own convictions as Christians, are challenged the most.
I may write a whole post on this later on. For now, enjoy the RELEVANT article.
Related Links:

Iraq War

Just War Theory

David Gushee