Two causes of world war ii were military build-up and hitler's invasion of small countries.

Well, this is true, but it is really over-simplifying the situation.

The war did not start because Hitler militarized Germany: the rest of Europe still hoped to avoid the war. But it was a step towards the war.

The same with the second option: The take over of Austria and Czekoslovakia were a step towards the war, but not a final one

the final one was Hitler's invasion of Poland, which is a big county.

He was probably very upset and disapointed and mad. all at once. so he probably wanted to show his disapointment, angryness, and depression. he didn't think of the affects due to the minor issue thst he has gone through. sorry if it doesn't . but i am trynna people.