A man stands in a sewage-filled street in Fallujah in 2010. The Fallujah wastewater treatment system was left unfinished more than four years past the initial deadline. The sewage facility is among hundreds of projects funded by U.S. taxpayers that remain abandoned or incomplete, wasting more than $5 billion, according to auditors. Hadi Mizban/AP hide caption

itoggle caption Hadi Mizban/AP

Richard Engel is NBC News' chief foreign correspondent. Dan Nelken/NBCU hide caption

itoggle caption Dan Nelken/NBCU

Army Pfc. Brayden Panttaja, 23, of Moscow, Idaho, walks past a pile of burning garbage while descending from a hilltop observation post at Combat Outpost Monti in Kunar province, Afghanistan, on Tuesday. David Goldman/AP hide caption

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Defense Secretary Leon Panetta is managing two wars in Afghanistan and Iraq, along with the fight against al-Qaida. Susan Walsh/AP hide caption

itoggle caption Susan Walsh/AP

Students play a basketball game on the campus of Iraq's Baghdad College, in this undated photograph. Ed Ou/The New York Times hide caption

itoggle caption Ed Ou/The New York Times

Neil Johnson, a University of Miami physicist, developed this mathematical formula to predict insurgent attacks in war zones. Courtesy of Neil Johnson hide caption

itoggle caption Courtesy of Neil Johnson