Now, secondly, does God command Christians to be pacifists?
First of all, God himself is no pacifist and does not wish peace to come to all people:
“Peace, peace to the far and the near, says the LORD; and I will heal them. But the wicked are like the tossing sea which cannot be calmed, And its waters cast up mud and filth. No peace for the wicked! says my God” (Isaiah 57:21).
“He judges and wages war in righteousness” (Rev 19:11).
However, one might argue that war and violence is to be waged by God alone, not his people. After all, vengeance is his (Rom 12:19) and we are commanded to turn the other cheek and love our enemies. While the Israelites were commanded by God to wage war, Jesus gives no such command and seems to prohibit violence. The closest Jesus himself came to violence is whipping the money-changers (Jn 2:14-16; see also Mk 11:15-16, Mt 21:12-13, Lk 19:45-46).
What about national self-defense? There is much to support it in the Old Testament. With regard to the New Testament, according to St. Augustine, while Jesus tells each of us to personally to turn the other cheek and offer no resistance to one who is evil, the state rightfully holds the sword that can be used in defense against evil:
“But if you do evil, be afraid, for it does not bear the sword without purpose; it is the servant of God to inflict wrath on the evildoer” (Rom 13:4).
Also, why does Jesus instruct his disciples to arm themselves if not to use them for some purpose? “[O]ne who does not have a sword should sell his cloak and buy one” (Lk 22:36).
In addition to these Scriptural supports, there is just war theory that was developed by the Catholic Church. Also, biblically and as well as historically, soldiers were not told to leave the army when they became Christians.
Therefore, Christianity, at least, does not advocate state pacifism. And if the Iraq War was waged in self-defense, then it was not a violation of Christian teaching.