The United States has replaced the top US and NATO commander in Afghanistan, General David McKiernan, less than a year after he took over the war effort there.
US Defence Secretary Robert Gates told reporters at the Pentagon that he believed a fresh approach was necessary at a time when the United States is changing its strategy for Afghanistan.
The Obama administration's new plan for Afghanistan and Pakistan calls for a military push to reverse deteriorating security, a surge of civilian aid and development assistance, and possible reconciliation between the Kabul government and some members of the Taliban.
Mr Gates said he had asked for General McKiernan's resignation and recommended Army Lieutenant General Stanley McChrystal, a former commander of special operations forces, to take over.
Lieutenant McChrystal is a former commander of special operations forces attuned to the style of counterinsurgency combat that the Obama administration has adopted as its strategy to thwart the Taliban and other militant groups.
General McKiernan is the chief architect of the current force build-up that is expected to more than double the number of US troops in Afghanistan to 68,000 by the end of the year. There were about 32,000 troops there at the end of December.
He has pushed for an additional 10,000 troops in 2010, a proposal that appeared to run afoul of Mr Gates who has expressed a reluctance to boost the force level beyond 68,000 troops.