The Soviet Union attacked Finland on November 30, 1939, and the Winter War began. The groundwork for this had been laid in the Molotov-Ribbentrop Pact of the previous August, when Stalin and Hitler agreed on spheres of influence in Europe and placed Finland in the Soviet sphere. The war ended in a bitter armistice in March 1940 that forced Finland to cede the Karelian Isthmus and other parts of its eastern provinces to the USSR.
Some post-war historians have argued that what Stalin got from Finland in the end was all he had really wanted to begin with. This viewpoint may still be held by those who see Stalin with rose-coloured glasses. The best way to refute it is to point to the words of Molotov himself in his meetings with Hitler in Berlin on November 12-13, 1940.
These meetings were held as a follow-up to the August 1939 pact and an attempt to confirm that its provisions were still in effect.
It is clear that Molotov’s primary (although not sole) concern was that, despite the Russian gains from the Winter War, the pact remained ‘unfulfilled‘ with regard to Finland. Time and again during the two days of meetings he returned to this theme, and sought assurances that Germany would not intervene if the Soviet Union finished the job.
Anyone who doubts that the goal of the Soviet Union was to occupy all of Finland need only read the transcript of these meetings. Molotov repeatedly seeks Germany’s blessing to complete the job in Finland. Hitler, who by then was planning his invasion of Russia, declared that he did not wish another war in the Baltic.
Finnish leaders knew of Molotov’s requests to ‘solve’ the Finnish question and understood what they meant. This played a leading role in driving Finland into Germany’s arms in the conflict with Russia that began in June 1941.
Excerpts (translated) from the transcript of the November meetings:
November 12, 1940, Molotov to Hitler: “The German-Russian agreement of last year could therefore be regarded as fulfilled, except for one point, namely, Finland. The Finnish question was still unsolved, and he asked the Führer to tell him whether the German-Russian agreement, as far as it concerned Finland, was still in force. In the opinion of the Soviet Government, no changes had occurred here. Also, in the opinion of the Soviet Government the German-Russian agreement of last year represented only a partial solution.”
Source: (full transcript available here)