When Germany invaded Poland, they declared on two economies that greatly exceeded their own. They managed to defeat France, but when they declared war on Russia and the US that number rose to three.
So Germany was fighting three nations with manpower and industry that dwarfed its own, even with the industries captured from other countries added in.
Japan was even worse off.
Talk about your poor planning. Sometimes I am amazed at how long they lasted. I guess that shows their understanding of the way to wage war. They were tactically brilliant, but strategically moronic.
Ha, you forgot the Italians.
They actually did more for our side, when they were part of The Axis.