Bad idea for 300 years. Don’t forget that the Swedes invaded Russia and were promptly exterminated about 300 years ago. Field Marshal Montgomery said that the two lessons of World War II were do not invade China and do not invade Russia.
The one exception was the Germans fighting on the Eastern front in WWI (not WWII). They actually captured quite a bit of Russian territory, including the Baltic States. They lost it when they signed the Armistance, however.