Why was the early aggression by germany not stopped( what is this called). what were some options to deter german aggression?

Before WWII Germany was granted some of their wants, and this was called appeasement. Appeasement was done because the Allies thought that if they gave in to some of their demands, it would keep Germany from doing anything major, such as war. The biggest concession was to allow Germany to take over the Sudetenland, which was in Czechoslovakia but inhabited by native German speakers that wanted to be allied with Hitler.