Final answer:
General Douglas MacArthur commanded the joint forces in South Korea during the Korean War. He was later relieved of his command due to disagreements with President Harry Truman regarding the war's conduct.
Step-by-step explanation:
Commander of Joint Forces in South Korea
The commander of the joint forces in South Korea during the Korean War was General Douglas MacArthur. He led the multinational United Nations forces that came to South Korea's aid when North Korean troops, under the direction of Kim Il Sung and emboldened by Soviet support, invaded the south with the intent to reunify the country under communist rule. President Harry Truman and the UN condemned the invasion, leading to the formation of the UN army to repel the aggressors.
After a period of defensive operations and a successful counter-attack at Inchon, MacArthur pushed the North Korean forces back. Despite initially having the support of President Truman, his commanding approach eventually led to discord, particularly regarding the crossing of the Yalu River and potential conflict with China.
Following disagreements with President Truman over the conduct of the war, and the public voicing of his views, MacArthur was relieved of command in April 1951.