The Pentagon announced that they are replacing the top American commander in Afghanistan, General David McKiernan. He's only been leading the troops for one year, but Secretary of Defense Robert Gates asked for his resignation. He will remain in his post until a new commander, most likely Lieutenant General Stanley McChrystal, can be nominated and confirmed. It's a major overhaul in military leadership in the midst of a war. For more we turn to BBC Security and Defense Correspondent Rob Watson.