A profile of the international terrorist network that the United States has singled out as the most serious threat to U.S. security.

President Obama vowed in January 2009 to close the prison camp at Guantanamo Bay. Two years later, the White House continues to face challenges to that promise, leaving critics to suggest the facilit…

U.S. and Western military officials are calling on Iran to help stabilize Afghanistan, but historic tensions and allegations of arming militants raise doubts about Tehran’s intent.