I think Eugenia has provided critical clues for the puzzle that is Boris.Following up w/inquiries she suggests is very important, but an accurate time line shouldbe established by making an inquiry thru Bad Arolsen. _________________________________________________
Additionally, Eugenia's find indicates that Boris was born in Samara.Samara Russian Orthodox Church Records are available on film thru LDS. _____________________________________________________
Rie, as a writer, you may be interested in reading"Surviving Lienz" by Anton Schleha.It discusses the psychological impact that the mystery and secrets had on DP (Displaced Person) descendants. If I remember correctly his father was part of the whole regiment that deserted.
Many POW's were placed in Hard Labor Camps. Bad Arolsen has amassed all those records and they are available to family. The major difference between the POW-Hard Labor Workers and the regular Ostarbeiter was they were fed but once a week, so many died of starvation.
Any foreigner who set foot in Germany (including territories held by Germany) is documented in Bad Arolsen.