Answer:
He was the commander of the UN forces sent to assist South Korea. He then became commander in chief of the United Nations Command and the South Korean forces.
Step-by-step explanation:
With the initial success, he defended South Korea of the invasion but then he went even further and attempt to invade North Korea. That provoke Chinese intervention and a series of major defeats after which he was removed from command by President Harry S. Truman.
I hope this answer helps you.