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

A woman at the protest holds a photograph of missing male relatives. Isra' al Rubei'i/NPR hide caption

itoggle caption Isra' al Rubei'i/NPR

The party of Shiite cleric Muqtada al-Sadr holds 40 out of 325 seats in Iraq's Parliament. Karim Kadim/AP hide caption

itoggle caption Karim Kadim/AP

Baghdad's traffic, choked by hundreds of checkpoints, slows to a crawl while security forces inspect vehicles for weapons and explosives. Lynsey Addario/National Geographic hide caption

itoggle caption Lynsey Addario/National Geographic

Iraqi demonstrators shout slogans during a weekly protest against corruption, unemployment and poor public services in the war-torn country at Baghdad's Tahrir Square on July 8. Mahmoud Othman, a Kurdish member of Parliament, says it's the Iraqi people who are losing out as a political stalemate continues. Ali al-Saadi/AFP/Getty Images hide caption

itoggle caption Ali al-Saadi/AFP/Getty Images

Secretary of Defense Leon Panetta sits with Gen. Lloyd Austin, the top U.S. commander in Iraq, as they fly in a Black Hawk helicopter over Baghdad on Monday. Paul J. Richards/AP hide caption

itoggle caption Paul J. Richards/AP

Air conditioners keep tents cool on a U.S. military base in Iraq. The tents have been treated with polyurethane foam to increase energy efficiency. Courtesy Steven Anderson hide caption

itoggle caption Courtesy Steven Anderson

Army Spc. Christopher B. Fishbeck of Buena Park, Calif., poses for a photo on a rooftop during his tour of duty in Iraq. Courtsey of Fishbeck's Family hide caption

itoggle caption Courtsey of Fishbeck's Family