what was Germany’s first major act of aggression under Hitler

The invasion of Poland

The annexation of the sudentenland

The invasion of czechoslovakia

The invasion of Austria

The first major act of aggression under Hitler was the annexation of the Sudetenland in 1938, which was part of Czechoslovakia. This was followed by the invasion of Austria in 1938 and then the invasion of Czechoslovakia in 1939. The invasion of Poland in 1939 marked the beginning of World War II.