North Korean forces experienced early successes, capturing the city of Seoul on June 28. Fearing the fall of the entire peninsula, General Douglas MacArthur, commander of U.S. forces in Asia, won Truman's approval to land U.S. troops on the peninsula. Rather than asking Congress for a declaration of war, Truman argued that the UN Resolution provided the presidency the constitutional power to deploy soldiers as a "police action" under the aegis of the UN. The intervention in Korea was widely popular in the United States at the time, and Truman's July 1950 request for $10 billion was approved almost unanimously. By August 1950, U.S. troops pouring into South Korea, along with American air strikes, stabilized the front around the Pusan Perimeter. Responding to criticism over unreadiness, Truman fired Secretary of Defense Louis Johnson and replaced him with the former Secretary of State George Marshall. With UN approval, Truman decided on a "rollback" policy—conquest of North Korea. UN forces launched a counterattack, scoring a stunning surprise victory with an amphibious landing at the Battle of Inchon that trapped most of the invaders. UN forces marched north, toward the Yalu River boundary with China, with the goal of reuniting Korea under UN auspices.