The Taliban have retaken control of Afghanistan after the longest US war in history. But why did the war start in the first place? How did it get to this point? And what impact will the new power have? Dr Keith Suter explains the history of the conflict, and why this is not only the closing of a chapter in US history, but the opening of a new one in global control of the country. 

See omnystudio.com/listener for privacy information.