Just five months after a team of Navy SEALS killed Osama bin Laden in Abbottabad, Pakistan, President Obama's administration claimed yet another kill Friday in its hunt for terrorists abroad. With the assassination of Anwar al-Awlaki, a U.S.-born cleric known as the "chief of external operations" for al-Qaeda in the Arabian Peninsula, new debate has arisen over whether it's appropriate for a president to order the killing of a U.S. citizen -- and how closely Obama's policies mirror those if his predecessor, George W. Bush.

Since taking office the president has overseen the killing of a remarkable number of terrorist leaders. Here are the most notable: