Max Boot, Jeane J. Kirkpatrick Senior Fellow for National Security Studies
The answer is simple: 9/11. The most costly terrorist attack ever was carried out from Afghanistan. The United States showed bipartisan determination to bring the perpetrators to justice and—the part that explains our continuing engagement in Afghanistan—to prevent its soil from ever being used again to stage terrorist attacks. This has been the rationale for a decade-plus attempt to build up Afghanistan's security forces so as to prevent the reemergence of al-Qaeda's close allies, the Taliban and the Haqqani network. That effort has made considerable progress: the Afghan security forces now number 350,000, and their professionalism has vastly improved. But the Taliban, secure in their Pakistan sanctuaries, remain a substantial threat, and the Afghans still need considerable help from the United States and other international partners to carry on the fight. That's why President Obama has vowed to maintain a train-and-assist mission even after the United States ends its combat role at the end of 2014.