Secretary Gates and Adm. Michael Mullen conduct a press briefing. Secretary of Defense Robert M. Gates (left) and Chairman of the Joint Chiefs of Staff Adm. Michael Mullen, U.S. Navy, conduct a press briefing where they announce Army Lt. Gen. Stanley McChrystal is to replace Army Gen. David D. McKierna as commander of NATO's International Security Assistance Force and U.S. forces in Afghanistan in the Pentagon on May 11, 2009. SHARE: Download: Full Size (0.06 MB) Credit: VIRIN: 140516-O-ADR34-774.jpg Photo Gallery