In the morning of 9 April 1940 Germany occupied Denmark and invaded Norway. This action took place to prevent the Franco-British occupation of Norway known as Plan R 4. Denmark and Norway did not really resist since they were told that the Wehrmacht would protect them against Franco-British aggression. The German navy which took part in the operation has lost a significant number of smaller and larger navy ships which was a significant blow. The German navy has never recovered from the losses caused by the British navy and air force. Operation “Weserübung” was a success for Germany but they paid a considerable price for it.
France felt protected by the Maginot Line and a considerably large army. When the Germans attack them at Mai 10th, they showed surprisingly little resistance. The tactic, later known as Blitzkrieg was an overwhelming success and France was defeated in a very short time with manageable losses. France which surrendered at June 22. The British Expeditionary Corps escaped over the channel after they were trapped in Dunkirk.
After the champagne in the west Germany invaded Romania. Hitler was at that time extremely popular with the German people. Germany, Italy, and Japan became closer allies forming the Axis. Italy invaded Egypt, Albania, and Greece. Italy declared war on June 10th to France and Great Britain. At that time the Germans were already deep in France with their army.
For months the Luftwaffe and Royal Air Force made raids. In fact, Germany failed to gain air superiority in the “Battle of Britain”. Therefore, the German operation “Seelöwe” the invasion of England could not take place.
The USA established Lend-Lease Act which means: The exchange of materiel aid then for 99-year leases on property to be used for foreign military bases. However, the American people did not want to go to war again.
If Hitler had stopped instigating wars at this point, it would have been very difficult to drive the Nazis out of the conquered territories. But Hitler was not only an unspeakable criminal but also a gambler. In the further timeline of history it became apparent that with the next campaigns the fronts were overstretched and the number of opponents increased.