Ya the Winter War! Russians really got the shit beat out of themselfs. They had more and better stuff, and the 1st move. Just no tactics or clothing, I heard some were sent in January wearing sailor shorts and scarves. Also this war didn't affect Op Barbarossa, Russian/German relations hadn't fallen through yet.
I've never heard of sailor shorts and scarves

People and even historians sometimes claim they only had summer clothes but that's not true. Their main issue was that they had autumn gear which work well during autumn and mild winters, but those long coats and wool shirts don't do much when temperatures start to hit -30C (-22F) and you'd need several layers of clothing to stay warm.