The video discusses how World War 2 began with Japan's invasion of Russia and continued with Germany's invasion of Poland, Italy's invasion of Albania, and Britain and France's war with Germany. The Phony War followed in which the Allies did little to stop the Germans. In 1939, the Allies landed troops in Norway in an attempt to help Finland and move them across Sweden to help Poland. The video introduces the concept of blitzkrieg, which is a tactic used by the Germans in World War II that involved their fast-moving tanks and troops. The Allies were initially successful in repelling the attacks, but eventually the Germans were able to land troops on British soil and begin bombing London. The Allies managed to hold off the Germans and eventually win the war.