This is a confusing answer. As part of the UN accords the DPRK/North Korea prisoners had to be repatriated, as did the ROK/South Korea prisoners. Many were. But Syngman Rhee took things in his own direction. In 1953 Rhee released thousands of prisoners who he claimed did not want to return to the DPRK/North Korea. He did this to protest the cease fire and armistice, and in part surely because he didn't want to send Koreans back to the DPRK. Rhee understood that this moment was his chance to unify Korea under his leadership. He didn't want to stand by idly while the Americans let it slip away. He released the prisoners to hopefully sabotage those negotiations, and keep the war going until his final victory. It certainly upset the Eisenhower administration that was trying to end the conflict.