I dealt with this topic briefly in my talk at the IAJGS Conference, "Donating your Family Papers? How, When, Where and Why". One of several discoveries in my father's papers was a letter he wrote in the summer of 1945 when, as an American GI, he visited his surviving family in Frankfurt at the end of the war. His cousin Sylvia, who was married to a non-Jew, had gone into hiding. Her sons served in the army, but were transferred to a non-combat division after their Jewish ancestry was discovered. Their aunt and grandmother (my great-grandmother's sister) were murdered.  While I don't know all the details of their story (wish I did), I suspect that their situation may have been more complex than assimilation as a motivation for service.

Karen S. Franklin
Yonkers, New York