Eurasia at the Eve of Operation Barbarossa

This is how Europe and Asia looked like on 21st June, 1941, just before Operation Barbarossa started. As we can see, Germany had conquered almost all of Europe defeating Czechoslovakia, Poland, Denmark, Norway, Belgium, the Netherlands, Luxemburg, France and Yugoslavia. German soldiers were also stationed in Finland, Greece and Northern Africa.

Italy, Germany's weak ally, was able to gain control over Albania, the Balkan coasts, Greece and Northern Africa (with substantial German help).

Other Axis powers that took part in Operation Barbarossa were Finland, Hungary, Romania and Slovakia.

Even though Nazi Germany and her allies controlled a huge amount of territories throughout continental Europe, an invasion of the USSR was necessary in order to conquer the oil deposits of the Caucasus. Oil was the main reason of this operation and a potential German victory would've meant the creation of several Reichskommissariats in Eastern Europe. Those were semi-colonial entities directly subjected to German rule whose aim was to achieve a German hegemony over continental Europe. Check the map I made some days ago if you want to deepen the German policy in the East in the so called "Generalplan Ost".