This is the second part of a three-episode series examining the post-9/11 world for the 20th anniversary of the al-Qaeda terrorist attacks.

The law of unintended consequences may explain why jihadists and "freedom fighters," as Ronald Reagan once referred to them, continue to haunt the U.S. in Afghanistan. Counterterrorism experts are warning Afghanistan will once again become a cradle for terrorism because of the U.S. withdrawal. But it is worth remembering how Afghanistan became a cauldron of jihadism in the first place. Anatol Lieven, who as a journalist traveled with the mujahideen during the late 1980s, discusses how foreign policy decisions under Presidents Carter and Reagan continue to cause problems today. In fact, some of the same warlords who benefited from U.S. covert support to fight the Soviets are still around. And it was Pakistan and Saudi Arabia, working with the U.S., who recruited tens of thousands of foreign jihadists to Afghanistan. One of them was Osama bin Laden.