As the offensive by the North Korean forces continued, General MacArthur had to admit that they were not as weak as he thought.
He came to a conclusion that the South Korean forces had already lost the defensive power, so it would be hard for them to repel the North Korean forces' advance, and that if they could not prevent the advance of the North Korean forces, they would have to conduct more difficult operations with a large number of troops and it would result in tremendous damage.
Therefore, he decided to commit the US troops to the battle line in series. However, due to North Korean forces' offensive, which was stronger than expected, General MacArthur's plan was postponed for long.
As the joint operation between the US and South Korea began, General Walton H. Walker established the 8th Army Command in Daegu on July 13, and the Army headquarters was relocated to Daegu to make cooperation with the UN forces.
As the UN forces were formed and the commanding system of the UN forces was streamlined, on July 14, President Lee Seung-man sent to General MacArthur a correspondence stating that he would delegate authority of conducting South Korean forces' operations to the Commander of the UN forces during the war.
On July 18, General MacArthur responded and said that he would accept it. This served as a cornerstone of the joint operation between the UN and South Korean forces.