Analysis of Iraq war testimony. Broadcast: Midday, 04/08/2008, 12:00 p.m. Two U.S. Senate committees are hearing testimony about the progress of the Iraq war from Gen. David Petraeus and Ambassador Ryan Crocker. Gen. David Petraeus, the top American commander in Baghdad tells a pair of Senate committees that a troop surge in Iraq has been successful, but that the success is fragile. Ambassador Ryan Crocker echoes Petraeus' concerns. During a break in the hearings, Midday hears some analysis from a foreign policy expert. Guest: Colin Kahl: Professor, Georgetown University Center for Peace and Security Studies. Fellow, Center for a New American Security.