For the American Left, there are many reasons to withdraw from Iraq: we're caught in the middle of a sectarian civil war, the Iraqi government is a perfidious ally, Iraq is a diversion from the real war against al Qaeda in Afghanistan, and so on. Some of these arguments are strategically shortsighted, others are based on false premises (such as the fact that the sectarian civil war is over in Iraq and bin Laden is in Pakistan, not Afghanistan), but at least they are more or less logically coherent. What makes almost no sense is the proposal that we turn...