The Nazi invasion tactic was known as the blitzkrieg, German for "lightning war". This strategy utilized all of the new and advancing technology that had come about by WWII. The German Air Force, the Luftwaffe, would first heavily bomb the enemy including dropping paratroopers. Then German Panzer divisions, or columns of tanks, would rush by to cleanup whatever enemy was left. Finally, standard troops would come in armored cars to hold the newly taken territory. The blitzkrieg was extremely fast and extremely effective, and this type of strategy very quickly took out Denmark, Norway, France, Belgium, the Netherlands, and most of eastern Europe including parts of Russia. Opposing forces had simply not drastically improved their military the way Germany had since WWI, and as such many nations fought against the Nazis the same way they fought against the Germans in WWI, which of course did not work.
