On Memorial Day, President Barack Obama announced his nomination for two top military positions. Army Gen. Martin Dempsey will replace Navy Adm. Michael Mullen as the new chairman of the Joint Chiefs of Staff. Dempsey would be joined in the Pentagon by Adm. James Winnefeld Jr., who would serve as his vice chairman. Also announced, Gen. Ray Odierno was picked to replace Dempsey as Army chief. These choices, especially Dempsey’s nod for the Joint Chiefs assignment, took many military watchers by surprise. For insight into the president’s decision, we speak with retired Army Colonel Peter Mansoor, an officer who served with both Dempsey and Ray Odierno. Mansoor is also the author of “Baghdad at Sunrise.”