The Korean War began on June 25, 1950, when North Korea invaded South Korea after Korea had been divided following Japan's surrender at the end of World War II, with the Soviet Union accepting Japan's surrender north of the 38th parallel and the United States south of it. What began as a civil war quickly became an international conflict as the Soviet Union and China supported North Korea while the United Nations, led chiefly by the United States, assisted South Korea. President Harry S. Truman treated the invasion as a test of the U.S. policy of containing communism and committed American forces under General Douglas MacArthur to what was called a United Nations police action without a formal declaration of war. North Korean forces rapidly drove South Korean and U.N. troops back to the Pusan area, but MacArthur's amphibious landing at Inchon on September 15, 1950, reversed the war, led to the recapture of Seoul, and allowed U.N. forces to restore the border at the 38th parallel. Encouraged by that success, the United Nations authorized troops to cross into North Korea in pursuit of a unified, independent, and democratic Korea, but after U.N. forces advanced deep into the north and captured Pyongyang, Chinese forces entered the war on November 25 and pushed them back south of the 38th parallel. MacArthur's public criticism of limits on the war led Truman to dismiss him on April 11, 1951, and under General Matthew B. Ridgway U.N. forces fought back to the 38th parallel by July 1951. For the next two years, the war settled into a bitter stalemate while peace talks continued, with prisoner exchange blocking agreement until 1953, when the Eisenhower administration's willingness to consider nuclear weapons and the Soviet decision to end aid to North Korea helped produce a settlement. An armistice signed on July 27, 1953, ended the fighting, created a 2.5-mile-wide demilitarized zone around the 38th parallel, and left Korea divided into two antagonistic states. The war cost approximately one million combined casualties, involved about 1.3 million Americans, killed more than thirty thousand of them, marked the first shooting conflict of the Cold War, and became America's first attempt to contain communism in Asia.