There a few defections (by few I mean very very few) by African Amerians during the Korea War. One example is that of Corporal Clarence Adams, who was captured by Chinese forces. Instead of being repatriated to the US at the end of the war, declared that he wanted to stay in China because of the racial discrimination (including Jim Crow) he faced in the US. He ended up working for Chinese foreign press and did propaganda broadcasts for Communist forces during the Vietnam War, telling black soldiers to defect. He eventually returned to the US during the cultural revolution and was dishonorably discharged.