There are many Christians who believe that under no circumstance is war justified in the Bible. In answering the above question, however, it’s important to realize that it is God who has established government within civilized society and one of the duties of government is to protect its citizens from those who would harm them. That's why we have laws and that's also why God has given governing authorities the right to bear the sword. (Romans 13:1-5)

Sadly, there are still governments within the world who, if given the opportunity, would not only kill their own citizens (as Saddam Hussein has done), but also enslave the citizens of other countries by conquest. These evil governments need to be restrained and quite often this is done by force when diplomacy fails to work. All we have to do is look at history to be reminded of what happens when nothing is done in the face of evil. Remember what Pol Pot did to the citizens of Cambodia after the Vietnam War. Also, remember what Saddam Hussein did to his citizens and the countries around him. We all are aware of what the Taliban (the fallen government in Afghanistan) did (they brutalized their citizens and protected Al Queida which exports terrorism to other countries). The worst thing a good person, or country, could do in the face of evil is to do nothing. (Proverbs 25:26)

Even though our desire is that evil governments change, history has shown that, quite often, this does not happen unless they are removed. No civilized person wants war, however, at times, it's thrust upon them through the evil actions of others.