Appeasement is a policy in which individuals/countries allow an aggressor to take action without stopping them. This policy helps to start World War II.
Appeasement was shown by many European countries in the 1930's when they made the Munich Agreement with Adolph Hitler. In this agreement, Hitler gained land in Czechslovakia that his army invaded. In return, Hitler promised not to invade any more territories. In this scenario, Hitler was the aggressor and countries like Great Britain and France were the ones allow Hitler to take action without stopping him. This act of appeasement inspired Hitler to invade other countries and territories, ultimately leading to World War II.