World War II was the culmination of a quarter century of tank development, and it would also be the first major test of tanks in mobile warfare, during which they had to face other tanks. However, many of the tanks were constructed with the static warfare of the Western Front in mind and were thus slow and had short operational ranges. Others were too light to face opposing tanks or the new generation of anti-tank weapons that hadn’t existed in World War I.

The unsuitability of these tank models for this new kind of warfare was quickly recognized, and the belligerent powers scrambled to create better designs. As each new, improved model came off the assembly lines, the opposing powers rushed to create a tank that could beat it. In that regard, World War II was also a war between rival engineers.

At the same time, German military officials were at the forefront of developing new ideologies when it came to utilizing their tanks to maximum effect. Heinz Guderian even published a book on the topic before becoming one of the Third Reich’s most effective tank commanders.

Moreover, during the German invasion of Poland, Nazi forces gained experience they would use across Europe and in Russia. After all, it was in Poland the Wehrmacht saw action for the first time, conducting what was not only an invasion, but also a trial run of its new equipment and tactics. The Polish invasion proved invaluable in providing the German high command with a low-risk, high-value live-fire exercise for their newly minted war machine, while the actual combat experience highlighted the remaining flaws in the system. During the campaign, the Germans honed tactics and weapon systems for the massive struggle with the Soviets, British, and US that loomed on the horizon.