'Hitler had one simple over-riding aim in foreign policy – expansion in the East. 'Explain why you agree or disagree with this statement.

I agree with this statement. Hitler had one aim of making Germany a great power again by acquiring Lebensraum (Living space) for Germans. He claimed that German population is constrained and more land was needed for them. The foreign policy of expansionism was a dominant idea and symbol of life of the nation. The hatred for Jewish Bolshevism made war on USSR unavoidable at some point of time. For this purpose, he did override the foreign policy by attempting to expand in land. He wanted to annex not only parts of Czechoslovakia, Poland and parts of Austria but also looked forward to take the Ural Montains which belonged to the Russians.
The manifestation of the same aim was bringing all German speaking areas under one Reich (Empire). The idea of pan Germanism was executed by first annexing Austria, then Sudetenland, Czechoslovakia and the attack on Poland which triggered the war. The next target would be USSR. All this was based on militarism and his belief that important issues can be solved on battlefield.