I believe whoever conceived and wrote Hogan's Heroes knew of
the real WWII prisoner secrets going on.
Soldiers were given codes and if captured kept Washington DC informed. Packages by fake church ladies groups were delivered with radio parts hidden in baseballs, escape handkerchief maps and other contraband.
Sure, they over-exaggerated with Hogan's Heroes to a great extent and had a lot of fun but they knew. They had to know. And only many years later did the rest of us know.
I have a copy of this great book.