During and around the time of World War 2 Finland engaged in a bitter defensive war against the Soviet Union, against all odds, and won. They also hammered the Germans out of Lapland in 1944.
But how did they do so well? Was it tactics or how their troops were trained? From what I know they were pretty under-equipped and hadn't nearly the same experience at war fighting as that of German or Russia.
/u/vonadler answered this (almost) same question a while ago:
Just a minor correction, Finland did not win the Winter War.