In 1940, Hitler indicated his switch to military conquest rather than annexation by invading

Let's see what happened before. Hitler annexed Austria before anything else. The Austrians didn't put up much opposition as it was Hitler's home country. Hitler later annexed Sudetenland, an area of Czechoslovakia where the majority was German. Although the Czechs opposed it (why wouldn't they), a treaty was signed by the Germans and other European countries to settle the case and to give Germany Sudetenland. Eventually, Hitler invaded and took over all of Czechoslovakia.