Juan Cole linked to this AP story, but I want to spread it around a bit more:

A series of secret U.S. war games in 1999 showed that an invasion and post-war administration of Iraq would require 400,000 troops, nearly three times the number there now.

And even then, the games showed, the country still had a chance of dissolving into chaos.

In the simulation, called Desert Crossing, 70 military, diplomatic and intelligence participants concluded the high troop levels would be needed to keep order, seal borders and take care of other security needs.

The documents came to light Saturday through a Freedom of Information Act request by George Washington University's National Security Archive, an independent research institute and library....

But Rumsfeld stamped his foot and said "Gee whiz" and "Golly gee," so everybody backed off. And besides, God had cushioned every fall the president had ever taken in his life, so nothing could possibly go wrong....