Nearly 20 years after the U.S. drove the Taliban from power in Afghanistan, the group claims it holds more territory that any time since the war began in 2001. As President Trump says he wants to end the war, FRONTLINE reporter Najibullah Quraishi goes on a dangerous journey inside both Taliban- and ISIS-held territory and exposes the harsh reality that not only is the Taliban once again wielding power, but the threat from ISIS looms large.