It existed in post-war Germany, as U.S. troops battled a rebellious population. That was in October 1945. Of course, the methods of terrorism – truck bombs, suicide bombers, etc. – were not yet fully perfected. But the idea that you can invade a country, topple a totalitarian dictatorship, disband the army and expect peace to break out overnight is preposterous. This is not to downplay the real problems in Iraq, but it is to put them in some kind of sane perspective.