Journalist Martin Smith, who covered the war in Afghanistan for two decades, recently interviewed US military and Taliban leaders to chronicle the war. Smith speaks with host Marco Werman about a new series of documentaries he made with Marcela Gaviria, America and the Taliban, for PBS FRONTLINE, on how the effort to eliminate al-Qaeda and oust its ruling ally, the Taliban, became America’s longest war — and how it ended in defeat in August 2021 with the withdrawal of US troops.