On 29 February 2020 in Doha, the United States signed an 'Agreement for Bringing Peace to Afghanistan' with the extremist Taliban movement. Yet on 15 August 2021, the Taliban seized control of Afghanistan's capital, Kabul. This article argues that the Doha Agreement did not simply precede the Taliban takeover; in significant ways it contributed to it. In its negotiation, content and implementation, it created destructive incentives for domestic and international parties, and it had effects on mass psychology in Afghanistan that its creators seemed not to have anticipated or understood. In that sense, it serves as a cautionary tale about the danger of assuming that negotiated 'diplomatic solutions' are necessarily superior to messy alternatives. The closest 20th-century equivalent was the Munich Agreement of September 1938.