When the United States led the invasion of Afghanistan in 2001, the mission was clear: retaliation against the Taliban government for offering safe haven to the masterminds of the 9/11 attacks.
Ten years later, the mission is no longer clear -- not to the American people, not to the Taliban, not to regional stakeholders, and unfortunately, not even to the nearly 100,000 American troops struggling to maintain a sense of purpose in some of the most forbidding terrain in the world. And the criticism and challenges to U.S. efforts in Afghanistan abound. What happened?