First disclosure: I am a biblical christian, meaning I do not follow the dictates of any church. Any orginize church is fundimentally flawed in that it becomes a tool of man and not God. The basic principle for a Biblical Christian is that the bible is more important than the church. We meet with other Christians, share teachings with them and others, but there is no organization. There are no religious leaders that I look to to tell me if a war is good, bad, just, or anything else.
1)The bible clearly allows a person to protect themselves and their family.
2)The bible clearly allows govenments certian rights that do not fall to single humans, one example would be the right of the state to use capital punishment, but that right is not granted to a singular human.
3)Since the coming of Christ, one thing that is not allowed is for you to raise your hand in violence in the name of Christ. This is something that the early Christians had right, and which quickly became perverted by "organized" churches.
Putting this all together, a war can be justified if it is fought by a state in defense. This defense is not limited to jsut the defense of your direct territory but can extend to a "pre-emptive" defensive action. Christians can fight in said war, if the war is such that the enemy poses a threat to him and his family and most of all that the war is NOT fought on religious grounds.
To use examples from history, and please understand these are my opinions and not anybody else's. Lets take the Civil War (as if any war can be civil). This war is unjust. Neither side was a serious threat to the other, and all of the issues could have been handled in a different manner. On the other hand, WWII is a just war because the enemy states posed threats to all the rest of the world, no matter where you lived. In both theaters, the opposing governments where out for domination and it would not have stopped with the gains they had made early on. They clearly needed to be stopped of the safety of mankind.
I purposely left out the current sittuation as the initial post requested this not be a flame war.
for you Mad Cow[boy]s and Socialist Stinkers.... 
Anyone who clicks the first one needs to read their Holy Text more closely. Anyone who clicks the last one is from a religion I've never heard of 
