The United States announced that a C.I.A. drone strike killed the Qaeda leader, a longtime ally of Osama bin Laden who was considered a mastermind of the Sept. 11 attacks. Here’s a guide to the strike and its implications.

The United States announced that a C.I.A. drone strike killed the Qaeda leader, a longtime ally of Osama bin Laden who was considered a mastermind of the Sept. 11 attacks. Here’s a guide to the strike and its implications.