Approved the raid that found and killed Osama bin Laden, set policy that U.S. would no longer use harsh interrogation techniques. Largely carried forward George W. Bush's key anti-terrorism policies, including detention of suspects at Guantanamo Bay despite promise to close the prison. Also has continued with military commissions instead of civilian courts for detainees and invocation of state secrets privilege in court. Expanded use of unmanned drone strikes against terrorist targets in Pakistan and Yemen.
(Photo: Eric J. TIlford/U.S. Navy/Getty Images)