I hope mods do not moderate this due to that word but it is a...

I hope mods do not moderate this due to that word but it is a serious question. I have just finished watching the DVD series on Australians at war and the question occurred to me. They portrayed the complexities and the horror of war. One is left with the desire that it does not happen again. However what does one do when the bad guys openly attack you, as in 9/11? Do you take notice of inane bumper stickers that say "make love not war" or some other comment and turn the other cheek? Or do you say "watch out!" Or what about a group that wants to wipe out your way of life, what do you do?

Does the idea of a "just war" still exist? What are the conditions for a just war at this time in history?