VICE PRESIDENTIAL GREETING Defense Secretary Robert M. Gates and Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, left, greet Vice President Joe Biden upon his arrival at the Pentagaon before the Armed Forces Farewell Tribute to honor the retiring secretary, June 30, 2011. SHARE: Download: Full Size (0.06 MB) Credit: VIRIN: 415284-R-KKW78-191.jpg Photo Gallery