Serling was never a POW. He was a paratrooper who fought in the Philippines, including in the block-to-block fighting for Manila. He was wounded three times, including one that wrecked his knee, and suffered some form of PTSD the rest of his life, but he was never a prisoner of the Japanese.
I guess I heard wrong. Donald Pleasance who played the Forger in the The Great Escape was a POW. Or so I heard.