The prime minister of Australia weighs in on Iraq. I found his basic statement of the doctrine of containment as applied to the Cold War, and the reason why it should not be applied today, very effective.
The view, validly held, was that because both sides had weapons of mass destruction, the potential human cost of military action by the West and the Soviet Union at the time of Hungary in 1956, or Czechoslovakia in 1968, would have been infinitely greater than the human cost (bad though it was) in leaving dictatorial Soviet-backed regimes in power there.
Then, the potential cost of doing something was greater than the cost of doing nothing. Now, in the case of Iraq, the potential cost of doing nothing is clearly much greater than the cost of doing something.
If Iraq isn’t effectively disarmed, not only could she use her chemical and biological weapons against her own people again and also other countries, but other rogue states will be encouraged to believe that they too can join the weapons of mass destruction league. Proliferation of chemical, biological and, indeed, nuclear weapons will multiply the likelihood of terrorist groups laying hands on such arms. The consequences for mankind would be horrific.