During WW2, the German and Russia side have both pressed some of their Captive POW to serve in their rank and file because of the war depleting their number. As a result, many former colonial conscript from British/French empire was pressed into serving The German Wehrmacht, including Algerian, Indian, Ukrainian and so on and number of Korean/Japanese and Hungarian was pressed into Red Army.
On the other hand, this is not the most complicated of that story there are history wise.
A Korean man have been fighting for 3 sides during WW2, this guy is
https://en.wikipedia.org/wiki/Yang_Kyoungjong
HE started fighting with the Japanese after he was conscripted into Imperial Japanese Army.
After fought in Russia, he was captured and pressed into the Red Army due to his colonial past.
And after he fought the German on the Eastern Front, he was once again captured and pressed into Wehrmacht.
He was finally captured on D-Day fighting the American, he was transfer to US, becoming a US Citizen after the war and died in Illinois