https://en.m.wikipedia.org/wiki/Winter_War
Technically it ended in a peace treaty, but Finland only gave up 11% of their land, when Russia intended to conquer all of it. I call that a win.
Russian forces outnumbered Finland's by 3 to 1, and had 30x as many vehicles. Finnish forces lasted much longer than Russia expected.
Suck it Sweden.
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Daily reminder that Finland fought with the [url=http://www.wikipedia.org/wiki/Godwin%27s_law]-godwinslaw!-[/url] against Russia in the Continuation War.