The actors who played German characters in Hogan’s Heroes served in the US military during WW2.
Colonel Wilhelm Klink (portrayed by Werner Klemperer)
Sergeant Hans Schultz (portrayed by John Banner)
General Albert Hans “Hansi” Burkhalter (portrayed by Leon Askin)
Major Wolfgang Hochstetter (portrayed by Howard Caine)
FYI: re “Hogan’s Heroes” - Jewish actors in it
* Leon Askin: Austrian refugee from Hitler; beaten by the SS in 1933 - (Gen. Burkhalter
)
*John Banner - refugee from Austria - (Sgt. Schultz)
*Werner Klemperer - refugee, Germany, son of famous orchestra conductor Otto Klemperer. - (Col. Klink)
*Robert Clary (prisoner Louis Lebeau). Polish Jew deported from France to Buchenwald concentration camp. Lost most of his family there.
Source: “The Forward”, a Jewish weekly newspaper (Forward.com), “Funny Nazis? The Return (In Bulk) of Hogan’s Heroes”, Benjamin Ivry, Jan. 19. 2010, among other articles.
Louis LeBeau - Robert Cary, Spent WWII in a concentration camp.
Schultz - John Banner also spent time in a camp, but it was still early in the regime, so he got out. And then bugged out.