Basically Finland asked for military assistance from Nazi Germany to keep the Soviet Union at bay. German troops fought the Soviets on Finnish soil. And then when the war turned sour for Germany, Finland turned against Germany and kicked them out - more or less at the behest of the United States.

Finland’s problem has always been its gigantic aggressive neighbor to the east - and it still has that problem today. It explained its cozy relationship with Nazi Germany by the need to keep a bigger problem at bay. And it was completely true and completely rational.

But what was also true - and I know it for a fact because I talked to Finns who lived through the war and housed Germans - is that the German troops behaved impeccably in Finland and left a very good impression, even today. The Finns aren’t too proud of that but it’s a fact, and it’s even understandable from the point of view of individual Finns of the time.

After the war, not wanting to lose a potential ally in the newly-established Cold War, the US sort of accepted Finland’s rationale and let it slide. Kind of like they did with France too, which equally deserved a lot more flak than they got.

https://en.wikipedia.org/wiki/Finland_in_World_War_II