evidence: Initially, this new strategy was a success. The Inch’on Landing, an amphibious assault at Inch’on, pushed the North Koreans out of Seoul and back to their side of the 38th parallel. But as American troops crossed the boundary and headed north toward the Yalu River, the border between North Korea and Communist China, the Chinese started to worry about protecting themselves from what they called "armed aggression against Chinese territory." Chinese leader Mao Zedong (1893-1976) sent troops to North Korea and warned the United States to keep away from the Yalu boundary unless it wanted full-scale war. [...] Finally, after more than two years of negotiations, the adversaries signed an armistice on July 27, 1953. The agreement allowed the POWs to stay where they liked; drew a new boundary near the 38th parallel that gave South Korea an extra 1,500 square miles of territory; and created a 2-mile-wide "demilitarized zone" that still exists today.