The Battle of Pusan Perimeter was a large-scale battle between United Nations and North Korean forces lasting from August 4 to September 18, 1950. It was one of the first major engagements of the Korean War. An army of 140,000 UN troops, having been pushed to the brink of defeat, were rallied to make a final stand against the invading North Korean army, 98,000 men strong.
UN forces, having been repeatedly defeated by the advancing North Koreans, were forced back to the "Pusan Perimeter", a 140-mile defensive line around an area on the southeastern tip of the Korean Peninsula that included the port of Pusan. The UN troops, consisting mostly of forces from the Republic of Korea, United States and United Kingdom mounted a last stand around the perimeter, fighting off repeated North Korean attacks for six weeks as they were engaged around the cities of Taegu, Masan, and P'ohang, and the Naktong River. The massive North Korean assaults were unsuccessful in forcing the United Nations troops back further from the perimeter, despite two major pushes in August and September.