Were American nuclear weapons ever based in South Korea?

The MGM-31A Pershing was the missile used in the Pershing 1 and Pershing 1a field artillery missile systems. It was a solid-fueled two-stage ballistic missile designed and built by Martin Marietta to replace the PGM-11 Redstone missile as the primary nuclear-capable theater-level weapon of the United States Army and replaced the MGM-1 Matador cruise missiles operated by the German Air Force. Pershing later replaced the MGM-13 Mace cruise missiles deployed by the United States Air Force and the German Air Force. Development began in 1958, with the first test missile fired in 1960, the Pershing 1 system deployed in 1963 and the improved Pershing 1a deployed in 1969. The U.S. Army replaced the Pershing 1a with the Pershing II Weapon System in 1983 while the German Air Force retained Pershing 1a until all Pershings were eliminated in 1991. The U.S. Army Missile Command (MICOM) managed the development and improvements while the Field Artillery Branch deployed the systems and developed tactical doctrine.

The 2nd Missile Battalion, 79th Artillery Regiment formed for deployment to South Korea in February 1964.