The change in command during a time of war is a testament to Gate's faith in McKiernan's leadership. While Gen. George Casey was replaced in Iraq by Petraeus in 2007, it was after two and a half years and Casey was then made chief of staff of the Army.
It also comes as 21,000 additional troops who McKiernan had requested to take on the Taliban in southern Afghanistan have begun arriving into the country.
Long considered an under-resourced campaign in the number of troops and equipment, by the end of this year the additional troops will boost U.S. troop strength to 68,000, which is more than double the size of the U.S. force there for much of last year.
But Gates said change was needed. "I believe resources or no, that our mission there requires new thinking and new approaches from our military leaders," he said.
Gates said today's announcement should not detract from the recognition McKiernan deserves for his long and distinguished military career. "For decades, in peace and war, Dave McKiernan has led hundreds of thousands of men and women in uniform with conviction, integrity and courage," he said. "He has dedicated his life to the preservation of the freedoms we in this nation enjoy. And on behalf of the Department of Defense and the nation, I thank him for his years of selfless service."
Time Magazine named McKiernan one of its Most Influential People for 2009. Writing for the magazine, retired NATO commander and U.S. Army Gen. Wesley Clark praised McKiernan's leadership and "smart thinking" in the NATO campaign in Kosovo, where he exhibited "a willingness to bring unpleasant news to his superiors," both skills Clark said he would draw upon to excel in Afghanistan.
In command of Joint Special Operations Command in Iraq and Afghanistan, McChrystal led special operations units, like Delta Force, that operated in some of the most secretive missions in pursuit of high-profile insurgents.
He had a controversial role in the awarding of the Silver Star to Army Ranger Pat Tillman after the former NFL star's death by friendly fire in Afghanistan.
An investigation concluded that he had made "inaccurate and misleading assertions" in some of the paperwork recommending Tillman for the Silver Star even though he already had information suggesting Tillman had died from friendly fire. The Army did not agree with the investigation's recommendation that he should face some kind of action for his actions.