They throw flowers at us as we leave

That is about the current state of the Pentagon's plan for any type of significant withdrawal from Iraq. Brad Plumer at the New Republic is passing along an excerpt from a National Journal article:

It's almost impossible for the military to seriously plan for a contingency -- withdrawal -- that the commander-in-chief won't even discuss....

Knowledgeable Pentagon sources say that some planning for a possible drawdown in Iraq is in the "conceptual" stage, but they concede that the vast majority of the military's energy and effort is focused on implementing the troop surge and Petraeus's counterinsurgency campaign in Baghdad. If the campaign is successful, it will certainly set the conditions for a more orderly withdrawal. Yet some experts recall a similar lack of serious advance planning for "Phase 4" stability operations in Iraq, even as the 2003 invasion loomed.

Withdrawing an army in good shape is a tremendously difficult task because there are few good roads, numerous natural choke points, massive synchronization problems in making sure that Unit A187 and Unit V75 are not trying to use the same road at the same time and finally in the Iraqi case if and when US units are engaged in a general withdrawal to Kuwait, Aquaba or Ceyhan, they'll be traveling through areas that are ready to intensify their civil war.

If I remember the 1994 and 1995 debate on the options for the EU peacekeeping/observation forces in Bosnia, the covered withdrawal plan for the 40,000 or so troops on the ground was anticipated to have needed the rapid introduction of an additional 50,000 troops to seize key choke points and a couple of carrier air groups for fighter cover. This planning process was for a much smaller force much closer to their logistics bases and going through non-hostile territory controlled by the Bosnian Muslims at the time.

It is this scenario that has led some Democrats to make statements that supported a firm deadline for withdrawal to also support a very temporary increase in troop numbers to safely withdraw the currently deployed force. The southern bridges in any hostile withdrawal scenario would need to be seized and held for a couple of weeks.

But the geniuses in the White House are convinced that if the US leaves, the Iraqi's will break out their strategic flower reserves and finally show their gratitude to us for ruining their country's ability to function as a quasi modern state.