Andrew Exum's take on the changing of the guard:
This tells me that President Obama, Secretary Gates, and Gen. Petraeus are as serious as a heart attack about a shift in strategy in Afghanistan and Pakistan. This was ruthless, and they were not about to do the George Casey thing whereby a commander is left in the theater long after he is considered to have grown ineffective.
The sad truth of the matter is that people have been calling for McKiernan's head for some time now. Many of the people with whom I have spoken do not think that McKiernan "gets" the war in Afghanistan -- or counterinsurgency warfare in general. There was very little confidence that -- with McKiernan in charge in Afghanistan -- we the United States had the varsity squad on the field.
That all changed today. I do not know if the war in Afghanistan is winnable. But I do know that Stan McChrystal is an automatic starter in anyone's line-up.