Final answer:
General Douglas MacArthur's bold plan to defeat the North Koreans was to launch an amphibious invasion of the coastal city of Inchon, which proved to be a turning point in the early phase of the Korean War.
Step-by-step explanation:
General Douglas MacArthur's bold plan to defeat the North Koreans was to launch an amphibious invasion of the coastal city of Inchon, located on the eastern side of the Korean peninsula. By attacking where the North Koreans least expected it, MacArthur aimed to drive a wedge through their supply lines and trap the invading army between Seoul and Pusan. This offensive proved to be a turning point in the early phase of the Korean War and allowed UN forces to push the North Koreans back across the 38th Parallel.