Who did McCarthy blame for the U. S.'s military performance in Korea?

Answer: President Truman

During the early days of the Korean War, McArthur had proven to be an excellent leader with brilliant strategies. However, he decided to invade North Korea in order to fully defeat the communists. Truman accepted, although he was worried about a Chinese intervention. McCarthy assured him this was very unlikely. However, the Chinese did intervene, and when McArthur asked for permission to attack China, Truman refused. The conflict was well-known, and resulted in Truman relieving General McArthur of his duties in Korea.