There's much more of those than you would think.
English and Germans fighting against the bolsheviks, immediately after WW1 in 1919 and 1920, Americans joining the SS and fight the Russians together with the Finns and staying there until 1945, stay-behind troops behind the WW2 russian steam roll and fighting as partisans (yes, also english and american ones), or germans who went, or were taken to, the USA, England and Russia after WW2.
Not so much black and white, and of course seldomly mentioned in those official history lessons.
