30 September 1938. Chamberlain steps off the plane at Heston waving a piece of paper, and the crowd loses its mind with relief, the most human thing in this story. Nobody who lived through 1914–1918 wants the sequel. Czechoslovakia's German-speaking borderland, the Sudetenland, has been signed away at a conference the Czechs were not invited to.
Why then
Britain and France remember the Somme, and their armies and air forces are not ready. Hitler took Austria in March without a shot and now claims to speak for three million Sudeten Germans. The Soviet Union, also allied to the Czechs, is left out of the room.
What they wanted
Chamberlain hopes for 'peace for our time'. Hitler wants the Sudetenland, and half wanted the war he was talked out of. Churchill, unbearable on the back benches, demands the shame be named before the war arrives anyway.
What changed
Czechoslovakia loses its border forts and its defensible frontier. In March 1939 German troops march into Prague, and appeasement is finished. Britain guarantees Poland.
Still argued
Did Munich buy a year to build radar and fighters, or teach Berlin that threats work? Churchill's memoir argued the second and set the verdict for a generation; later historians stress how unready Britain really was.