Questions that should be answered in making US policy for Iraq

I have refrained from posting on the subject of Iraq since I could not add substantively to the debate. Today, however, I post two issues that should be addressed by those advocating policies for Iraq, especially those advocating precipitous withdrawl:

• How great is the probability of genocidal ethnic cleansing in Iraq if the U.S. pulls out precipitously? The coercive government of Saddam Husein at least kept the peoples of Iraq from such a course. If the U.S. invasion and departure create the conditions leading to something even worse than what is going on now......?
• How great is the probability of chaos in the region if the U.S. pulls out precipitously? Is there a real possibility of widespread violence between factions headed respectively by Shiite Iran and Iraq and Sunni Saudi Arabia? What would be the implications of precipitous withdrawal for Israel and Palestine, Lebanon, oil (and European, Chinese and Japanese supplies), internal affairs in other Arab and Muslim nations, Pakistan, Afghanistan, the Central Asian states of the former Soviet Union, etc.?