Why did the Soviet Union invade Finland?

During the 1930s, Stalin long couldn't make up his mind about who was the worst danger to him: the Nazis, or our future WWII allies Great Britain and France. read more

Now, why did Soviet Union invaded Finland - Stalin was afraid that in case Finland side with germany Russian border would be toooo close to Leningrad(St.petersburg) - second largest city in USSR - the border before Winter war was in Beloostrov - 30 km. from Leningrad - in case of attack the city would be difficult to protect and also it was possible to shell it even without crossing Soviet border - right from Finnish territory. read more

I'd like to know a better answer, and hope this starter will provoke one. There could be two reasons: (a) The Soviets were nervous, in the late 1930s,. read more