"Well, there was actually no need for Hitler to go to war at all in 1939, Ebbie. What about that possibility? What if he had simply rebuilt the German economy and armed forces, but stopped short of attacking Poland or anyone else? What then?"

Actually there was every need for Germany to invade Poland in 1939. First of all, due to the crackpot economics of Nazism, the only way they could stay in power, and keep the German people on board, was by invading and looting other countries. (See Hitler's Benficiaries; Plunder, Racial War, and the Nazi Welfare State. Götz Aly. Metropolitan Books. New York. 2005.)

Secondly, the Nazi's long term aim was to overrun the USSR, thereby establishing an empire big enough to enable Germany to live off the fat of the Russian Land.