Appeasement led to more aggression prior to the start of World War II. This policy had the opposite effect of what it was intended to do. Appeasement means to give into demands now in return for a future promise. The key part of appeasement is that the country or the person gets what is being requested without having to work to earn it. All that has to be done is to make a promise to do something after getting what is being requested.
In 1938, when Hitler wanted the Sudetenland, he promised the Allies this would be his last request for land if they would grant this request. The Allies trusted Hitler, believing he would keep his word. However, Hitler didn’t have to do anything to earn what he wanted. All he had to say was he wouldn’t ask for more land. There was no stipulation of what would happen if he broke this promise.
Considering Hitler’s previous actions in Europe in the mid-1930s, the Allies shouldn’t have been surprised when Hitler broke his promise and took the rest of Czechoslovakia in 1939. After all, Hitler had been aggressive in the past, and very little was done about that. In his mind, he planned to stay aggressive regardless of any promises he had made. Appeasement often fails because a person doesn’t have to work to earn what he/she wants to get. After Hitler broke his promise, the Allies said any more aggression would lead to war. When Poland was invaded in September 1939, World War II began.