Playing Devil's Advocate...an apologia for pacifism
Another way to look at the war is in a "Pascal's Wager" sort of way. Worst case, if we would've followed the Vatican's approach, we would not have fought the first Gulf War. Saddam would rake in the oil revenues of Kuwait and Saudi Arabia and be able to buy nuclear weapons. He would own the Middle East. Millions are killed. (Again, this is the worst case scenerio).
We know the soul is infinitely more valuable than the body. And so Judgment Day comes and the accounting. Any fault imputed to you for your failure to act (i.e. to advocate war) would be mitigated by the following of the Holy Father's counsel. Whereas if you had taken the opposite approach and acted, you would be under even greater judgment for having spurned his counsel. For the Christian, there seems to be no cost, in strictly spiritual terms, of failing to go to war while there is a great cost if you are wrong. Were the early Christian martyrs wrong for leaving their children orphaned? I think not.
If one really and truly believes this life is merely a short stay at a bad motel and that heaven awaits, then one sees the soul as of infinite worth, the body little. All Christians were pacifists for the first couple hundred years. It might've been when they realized that the Second Coming was not going to be tomorrow exactly, that Christians became more "practical" in accomodating ourselves to the "real" world. Or perhaps it was a realization that every era is different, and that there is a time for war and a time for pacifism.