The answer is Europe.
From 1939-1940, the Nazi Germany army had an incredible amount of success taking over countries like France, Italy, Denmark, etc. The success of the Nazi German army could be contributed to their military tactics, especially blitzkrieg. Blitzkrieg means "lightning warfare" and represents how fast and how hard the German army attacked other countries.
By 1940, Great Britain stood pretty much by themselves, as they were the only country to not be invaded/taken over by the Nazi army.