system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why was a country as small as Germany so effective in WW2?

I've never understood why a country as relatively small as Germany was so devastatingly effective during World War II. Germany at one point was winning the war against much of Europe and Russia with its millions and millions of soldiers, yet surely the population and resources of all those countries combined with a far exceeded that of Germany. 

How was this possible; was all just down to good military strategy?
gpt
First of all Germany wasn't that small. It had the second largest population after Russia. This is especially so after it had absorbed Austria and parts of Czechoslovakia. 

Secondly, Germany was more industrialized than, say, Russia, with better infrastructure. To put it simply, it was wealthier and more developed. 

Third, the German military was more efficient, with better tactics and strategy. Other belligerents were poorly prepared for the mobile, dynamic warfare - they were still mostly thinking in terms of the static, immobile warfare of WWI. 

Lastly, Germany was able to fight its enemies one at a time rather than all at once. Poland fell almost immediately before anyone could do anything. Denmark and Norway also fell before the allies could adequately respond. Next, Germany invaded France and defeated them rather easily. This might be a bit surprising but neither the Soviets nor the US were still in the war. So Germany was able to conquer half of Europe without fighting Russia. When Germany invaded Russia, they simply caught them by surprise - the Red Army was very unprepared for the invasion and suffered horrible losses. It was only after the Germans failed to quickly knock out Russia that the war entered the attrition phase where the superior resources became a major factor.