A U.S. soldier, part of the NATO-led International Security Assistance Force, stands outside a military base in Panjwai, Kandahar province, south of Kabul, on Sunday. Allauddin Khan/AP hide caption

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Iran's supreme leader, Ayatollah Ali Khamenei, addresses a meeting in Tehran on Thursday. Khamenei is a staunch defender of Iran's nuclear program. AFP/Getty Images hide caption

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Lt. Col. Mark Schmitt, who will be among a group of U.S. military trainers heading to Afghanistan soon, calls out orders during a mock attack on the model Afghan village at the U.S. military base in Fort Polk, La. David Gilkey/NPR hide caption

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The latest violence in Afghan has raised doubts about the U.S. strategy. Here, Afghan demonstrators shout anti-U.S. slogans as they carry a wounded man during a protest in the Western city of Herat on Feb. 24. Aref Karimi /AFP/Getty Images hide caption

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Defense Secretary Leon Panetta (right) and Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey listen to questions during a Senate Armed Services Committee hearing on Capitol Hill Tuesday. Both men spoke about the U.S. military shifting its focus to Asia. Mark Wilson/Getty Images hide caption

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The U.S. military wants Afghan troops to begin taking the lead role in combat operations. Here, Afghan cadets who are joining the army are shown at their graduation ceremony on Dec. 18 in the northern city of Mazar-i-Sharif. Qais Usyan/AFP/Getty Images hide caption

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The chairman of the U.S. Joint Chiefs of Staff, Gen. Martin Dempsey (left), is in Israel to talk about the growing tension with Iran. Here, Dempsey speaks with Israel's top military officer, Lt. Gen. Benjamin Gantz, during a meeting at NATO headquarters in Brussels on Wednesday. Virginia Mayo/AP hide caption

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