As the son of a World War II veteran on the European front, I was taught much about the war, often more than I wanted to know. As an economist, I have always wondered how anybody could have been naive enough to think Germany had the resources to win. At the beginning of the war, the U.S. economy was already twice the size of the German economy. By 1943, we were four times bigger. And, that doesn't include the allies of England or France.
I've just finished "The Wages of Destruction" by Adam Tooze, which I think is the first economic perspective on that war. It traces the huge shift in economic resources starting in 1933 from civilian use to re-armament, describing it as "the largest transfer of resources ever undertaken by a capitalist state in peacetime." Yet, Hitler had concluded by 1939 that they could never hope to win a sustained war, as our combined economies would soon overwhelm his own.
So, why did he launch the war anyway? Because he believed it was inevitable, since Jews had taken over America! The only chance for German race to survive long term was for Hitler to win a quick peace. He envied England, a small nation with a vibrant economy because they had used military force to create an empire. Hitler wanted to create "living space" for the German people, taking enough land that the German people could live without fear of the Jews.
The triggering moment in 1939 when the balance of payments for Germany became so bad that the bond vigilantes attacked, dumping German bonds. Then, nobody would export to Germany without prior payment. At that point, he could no longer import the materials needed to increase his military force. Since his military would never be any stronger, that was the time to invade Poland and launch a quick war.
The book is a ponderous read but does show the importance of economic changes on political decisions.