The Soviet Union gradually released some POWs throughout the next few decades , but some did not return until the collapse of the Soviet Union in the 1990s .
Others who had settled and started families in the Soviet Union opted to remain .
The Soviet Union gradually released some POWs throughout the next few decades , but some did not return until the collapse of the Soviet Union in the 1990s , while others who had settled and started families in the Soviet Union opted to remain .