The belief behind appeasement was done to avoid another calamity such as the First World War. Leaders such as Chamberlain of England were convinced that the atrocities of the First World War should be avoided at all costs. Reeling in from the chaos and undermining of faith, Europe was shattered in geographic, financial, and emotional terms. All nations felt to a certain extent that the paradigm with which they viewed the world at the start of the conflict was severely undermined by it. The policy of appeasement struck at this very essence for it sought to avoid war at all costs. If this meant dealing with terms articulated by Hitler at the time, it was seen as a needed sacrifice. At the time, Hitler was not seen as the universal symbol of threatening evil that he is seen as now. The belief was that containing him was an acceptable risk if it prevented another entry into widened conflict. Bearing this in mind, it became nearly impossible to stop him when all leaders realized the existential threat he posed. This would mean that the policy of appeasement, a hope to avoid war, actually had much to do with a new one starting.
It is not correct to say that the followed this policy during WWII -- it is only correct to say that the followed it before WWII. By following it, they helped cause the war.
There are a few major reasons why they did this:
- They were tired out from WWI and did not want another war. WWI was so hard on England and France that they wanted no part of another war.
- In addition to this, the things Hitler was doing were being done to countries they didn't really care about. Who cares if Austria becomes part of Germany? Or if the Sudetenland does? It didn't seem worth fighting over.
- Many among the Allies believed that the Treaty of Versailles had been too harsh on Germany. So when Hitler started going against the treaty (putting military in the Rhineland, for example) they just felt that he was acting in an understandable manner because he was opposing an unjust treaty.
The popular take on appeasement was that Great Britain was simply trying to avoid war with Hitler but the reality of the times were that Great Britain and everybody else in the world knew that the election of Hitler would eventually lead to war. Great Britain used appeasement to buy time and allow themselves to prepare for war. It was a policy of delaying the inevitable, which at the time made sense but in light of how horrific Hitler’s policies were, seems like a monumental mistake.
The UK archives have a great lesson plan on this located here