Winter War, even I first was thinking the final clashes of the Continuation War in summer 1944, when Soviet forces were more trained, had much better commanders and still superior forces in both numbers and supplies. In winter war they had even greater superior in supplies, because Finnish army in 1939 didn't have even gun for all men or uniform. The "uniform" of usual civilian winter equipment and cockade is famous known as "Model Cajander" by our then-in-charge Prime Minister Cajander.
In winter war we truly were alone, with even Swedes staying out of war and giving just limited support. Western Allies couldn't help and it is much doubted that if they ever wouldn't come to fight to support us. With certain lose in sight, the thing that saved us was time. With Stalin shamed he over-thrown "The Goverment of Terijoki", which was supposed to become Stalin puppet-gowerment in Soviet regime of Finland, including fanatical communists who had escaped into Soviet Union after Civil War in 1918 and who survived Stalin's massacre in 1930's. Even treaty was hard for Finland and usually called as "Häpeärauha" (~shamed peace) our highest leaders were then informed by Göring that Germany may give us our revenge in time.
After Winter War, when Germany took control of Denmark and Norway, we had to either be finally annexed by Soviets or seek support from Germany. And in 1944 support from Germany was one thing that supported our brave soldiers to stop Soviets advancing into our homeland.
Also I have to mention that Mannerheim lead us in our all wars, in Civil War as leader of White Army and in Winter War anf in Continuation War as Commander-in-Chief. At the end of Continuation War he was elected as President of the Republic of Finland, still staying as Command-in-Chief until end of 1944 and so during a Lappland War.
Also I have mention that our national population during WWII was much less than 10 million, it was less than 4 million. I remember that my history teacher onced mention that we raised the Greatest Army in propotion of population, more than a half million and with best quality 8)
It is also always nice to speak with veterans, I have meet lot of them during my short life. My own grandmother also sometimes talk about wartime. She was in Lotta-organization (women in homefront did very much important work in peace and in war).
Well, about that's it this time. German efforts in the beginning of WWII have always had great impact for me, but at least they hadn't took a fight against opponent which one has almost everything 1:50 against them