You never really hear about the Soviet Union doing anything in WWII pre-Barbarossa, so did they have any direct conflicts with the Allies?
You may be interested in this question that was asked about a month ago
Well pre-Barbarossa, the Soviets and Nazis made the Molotov-Ribbentrop Pact which divided up Eastern Europe between them. Romania, Poland, Lithuania, Latvia, Estonia, and Finland were parceled up between Germany and Soviet Union. These areas weren't controlled by the Soviet Union when the pact was signed. For example, Poland was a free state that was an ally of Britain at the time (the Anglo-British alliance). The German invasion of Poland, was of course a very famous act with large consequences. But the Soviets also invaded parts of Poland from the East. Therefore, this was a battle directly against the Allies just as the war got underway in Europe.