On June 25, 1950, North Korean troops began the Korean War by invading South Korea. Two days later, the United Nations Security Council called on member nations to help defend South Korea, and 16 nations sent troops, with over 90 percent of them American. By September, United Nations forces had been pushed back to the Pusan Perimeter, but on September 15, 1950, they landed at Inchon, cut off North Korean forces in the south, and advanced to the Yalu River on the border with China. China, uneasy with United Nations forces on its border, entered the war and drove them south of the 38th Parallel. Truce talks began in July 1951, and in July 1953 the two sides signed an armistice ending the war. Deaths totaled 36,568 and wounds 103,284.