SHARING A MOMENT President Barack Obama, left, shares a moment with Navy Adm. Mike Mullen, outgoing chairman of the Joint Chiefs of Staff, during the Chairman of the Joint Chiefs of Staff change of responsibility ceremony on Joint Base Myer-Henderson Hall, Va., Sept. 30, 2011. Mullen was succeeded by Army Gen. Martin E. Dempsey, who became the18th chairman of the Joint Chiefs of Staff, during the ceremony. SHARE: Download: Full Size (0.05 MB) Credit: VIRIN: 391695-S-HNH38-807.jpg Photo Gallery