Hitler's invasion of the in June 1941 proved that he would consistently break agreements.

If this a true or false question, its true. the treaty of Versailles restricted any country from invading one another. Hitler invading Poland broke that agreement.

In July 1940, just weeks after the German conquest of France and the Low Countries, Hitler decided to attack the Soviet Union within the following year. On December 18, 1940, he signed Directive 21 (code-named Operation "Barbarossa"), the first operational order for the invasion of the Soviet Union.