Right now, President Obama is in India, showing solidarity with the world's largest democracy and doing presidential things like going to Mumbai and sleeping over at the location of the November 26, 2008 terrorist attacks. It's widely acknowledged that Islamic militants from Pakistan were responsible for the bombings, and that one of the plotters in that attack was an American small-time drug dealer named David Headley. He arrived in Pakistan in late 2001. How did he get there?
The Times explains that he was sent shortly after 9/11 to help with some cases, and they ignored signs that he was sympathetic to radical groups:
The October 2001 warning was dismissed, the authorities said, as the ire of a jilted girlfriend and for lack of proof. Less than a month later, those concerns did not come up when a federal court in New York granted Mr. Headley an early release from probation so that he could be sent to work for the United States Drug Enforcement Administration in Pakistan. It is unclear what Mr. Headley was supposed to do in Pakistan for the Americans.
He spent the next few years training with Lashkar-e-Taiba, the Pakistani group behind the attacks.