WaPo reports the results of a U.S. military war game:
1. "Majority Shiites would drive Sunnis out of ethnically mixed areas west to Anbar province."
2. "Southern Iraq would erupt in civil war between Shiite groups."
3. "[T]he Kurdish north would solidify its borders and invite a U.S. troop presence there."
In other words, the country would break into three parts. According to the man who ran the game, it would be "ugly" but not "apocalyptic."