By August 1950 the North Korean Army had overrun most of the Korean peninsula, and was advancing rapidly toward Pusan, the last open port in South Korea.The US Army hastily formed a perimeter along the arcing Naktong River to stop ? or at least delay ? the final North Korean breakthrough.Every available US unit in Korea, including a Marine brigade, was thrown into the fight against three North Korean infantry divisions converging to crush what became known as the ?Naktong Bulge..