After the fall of Col. Moammar Gadhafi in 2011, Libyan tensions fired up, and embassies were abandoned. Then, on Sept. 11, 2012, heavily armed Islamist militants launched an organized attack on the U.S. diplomatic mission in Benghazi. Four Americans were killed: U.S. Ambassador Christopher Stevens, Navy SEALs Tyrone Woods and Glen Doherty and State Department computer expert Sean Smith. Six CIA contractors defied orders to defend the compound. Thirteen hours later, only four of them were still alive, but they had saved more than two dozen fellow Americans. When the heroes returned home, then-Secretary of State Hillary Clinton and President...