Yes, this is a true story. Defectors, even high ranking Army officers, fought with the US. It is a winding tail of circumstances so it would make for a great movie.

FYI, there where quite a few army officers that hated the SS. Particularly the career officers. The regular army would drive enemy soldiers out of a town and move on. On their heals was the SS that stayed to oppress the people. This was dishonorable in the eyes of a Prussian trained officer.

https://youtu.be/IRx7KkrT1QU