Continuity mistake: When Helga brings in Klink's dinner and sits it down, Klink takes off his monocle. In the close up, it's on and his hands are folded, then he points to a chess piece, contemplating a move. In the wide shot, he's holding his monocle, and puts it on.
Continuity mistake: Col Hogan eats Col Klink's chicken leg and places it back on the plate with meat still on the bone. When Col Klink picks up the chicken leg after, there is no meat on the bone. It's stripped bare. (00:01:00 - 00:03:00)
Continuity mistake: When Hogan drinks Klink's wine, he picks up the glass with his right hand and his left arm is behind him. A second later, Hogan's left hand is in front of his chest.
Answer: The core POWs regularly escaped the prison camp but they made it their mission to conduct espionage and commit sabotage in the surrounding German territory. They also collaborated with different underground resistance groups and used a network of secret tunnels to help prisoners from other POW camps to escape, who then relayed vital information back to the Allied forces. Hogan and his men maintained the illusion that Stalag 13 had never had any prisoners escape in order to avoid their covert operations being shut down. Being that the prison camp is set in Germany during WWII, there were no American embassies.
raywest
Hogan has mentioned to different characters that they are actually stationed at Stalag 13 to help allied soldiers and prisoners from other Stalags to escape Germany.