I did not know about this history.
During the 1940 war between Finland and Russia, known here as the Winter War, Finnish Jews fought alongside their countrymen. But most surprising to those unfamiliar with this nation’s Jewish community could be the fact that Finnish Jews fought in World War II alongside Germany on the Russian front, as their country allied itself with the Nazis.
Even more unusual, the Finnish government afforded Jews full civil rights throughout the war despite strong pressure from the Nazis. Today’s community has a memory of a “field synagogue” built by Finnish soldiers in which they could conduct services alongside SS units.
Most interesting, perhaps, is another local story of a Jewish soldier who defied death to rescue a battalion of SS soldiers pinned down by enemy fire. Offered an Iron Cross he refused, in flawless German.
When a German officer asked where he learned to speak so well, the soldier reportedly answered that he was Jewish, and that since Yiddish was his mother language, it was easy for him to speak German. He then marched out of the deathly silent tent. The Finnish government supported his refusal of the award.
The Jewishness of these soldiers was not hidden from the Germans, and there even was a field synagogue. Furloughs were given for Sabbaths, and some came from considerable distances to attend. The Germans were aware of the synagogue but did not interfere (Rautkallio, Aseveljeys 127, 129–132). Some of the Jewish soldiers even liked to proclaim their religion to provoke the Germans, whose reactions were mainly surprised but not particularly negative. When asked about their Jewish soldiers, Finnish superiors usually defended them, saying they were no different from other Finns (Rautkallio, Aseveljeys 128–129). Jewish medical officers treated German patients and saved their lives, even risking their own (Rautkallio, Aseveljeys 133, 141). Several Jews were awarded German decorations, but they refused to accept them (Poljakoff in Torvinen, Kadimah 135; Smolar 155–57).
Update: Ilya Somin writes in with a correction:
There is a factual error here. Finland and Germany were not allied during the 1939-40 Winter War (when the USSR invaded Finland while the Nazi-Soviet Pact was still in force and Germany backed the Soviets), but during what Finns call the 1941-44 Continuation War (when Finland took advantage of Germany’s invasion of the USSR to retake the territory the Soviets had seized from them during the Winter War).