I know I read something about Russia wanting to reclaim the land but can't remember where or what it was!
The secret protocol of the Molotov-Ribbentrop pact is maybe what you're looking for.
Well during the war they did make up a puppet government to represent "the real will of the Finnish people" whom they were only helping against the fascists (the real government).
http://en.wikipedia.org/wiki/Finnish_Democratic_Republic