Fighting in cities is a totally different endeavor than obviously fighting out in the open.

Progress in Iraq has always been about teams of people and teams of teams - and ultimately about young men and women, Iraqi as well as people from the coalition.

US Ambassador to Iraq Ryan Crocker and I have repeatedly sought to emphasize that the progress in Iraq is fragile and also, possibly, reversible.

Al-Qaida in particular remains dangerous, and there [in Iraq] is some residual militia and special group presence. There are still between 20 and 30 attacks per day, still periodic car bombs and still loss of innocent civilians.

Over the last few years they have done a superb job in their fight against al-Qaida. As you may recall, our embassy in Jedda (in Saudi Arabia) was overrun some four years ago and a number of foreign workers went home because of violence against them.

There are some ideas that will translate from Iraq to Afghanistan and there are many that will not. The first lesson of counterinsurgency, in fact, is that every situation is truly unique, has its own context, its own specific set of factors - and you have to understand that context in enormous detail to be able to craft a sound and comprehensive approach.

This cannot be the United States being the air force for Shia militias, or a Shia on Sunni Arab fight.