A. Chamberlain's appeasement of Hitler at Munich.
Chamberlain governed Britain before WWII, and World War One was still fresh in the minds of his citizens, who had lost fathers, sons, brothers and comrades, with many men coming back without limbs, or with PTSD or "shellshock". Chamberlain's main concern was to avoid another war at all costs, by allowing Hitler's Germany to break many rules of their constraints, enforced by the Treaty of Versailles. Chamberlain resigned once he realized war was imminent, and Churchill took office, having believed that Appeasement was shameful and ineffective.