President Truman fired General MacArthur for insubordination. Although Truman was committed to waging a limited war in Korea, preferring to negotiate with China and North Korea rather than expand hostilities, MacArthur openly disagreed with the president and threatened to attack China if it did not agree to terms of peace.
When North Korea invaded South Korea in 1950, the United Nations authorized intervention. MacArthur, who was based in Tokyo while supervising the reconstruction of Japan after World War II, was chosen as commander-in-chief of the U.N. forces. While part of the U.N. army was pinned down in the southeast corner of the Korean peninsula called the Pusan Perimeter, MacArthur staged a water landing at Inchon, halfway up the peninsula, to capture the South Korean capital city of Seoul. When the North Korean troops retreated, instead of holding at the 38th parallel, the treaty-delegated border between North and South Korea, MacArthur ordered the army to follow them north. As a result, large numbers of Chinese soldiers crossed the border and joined the North Korean war effort.
To counter the Chinese attack, MacArthur suggested bombing China and enlisting troops from the Chinese nationalist government on Taiwan, but Truman was determined to contain the Chinese and seek a diplomatic solution. MacArthur was extremely vocal in his disagreements with his Commander-in-Chief, the president, until Truman relieved him of duty and appointed General Matthew Ridgeway as the new commander over the U.N. forces.