The Nakdonggang River or Nakdonggang () is the longest river in South Korea, and passes through major cities such as Daegu and Busan. It takes its name from its role as the eastern border of the Gaya confederacy during Korea's Three Kingdoms Era. Geography The Nakdonggang flows from the Taebaek Mountains to the South Sea or Korean Strait, which separates Korea from Japan. The river originates from the junction of the Cheolamcheon and Hwangjicheon streams in Dongjeom-dong, Taebaek city, Gangwon province. From there to its mouth it winds for about . The width of the river ranges from only a few metres in its upper reaches, to several hundred metres towards its estuary. Major tributaries include the Yeong, Geumho, and Nam rivers. Together with its tributaries, the Nakdonggang drains most of North Gyeongsang and South Gyeongsang provinces, along with small portions of North Jeolla, South Jeolla, and Gangwon. The total watershed is . History The Nakdonggang River has played an important role throughout Korean history. The river basin has been a favored dwelling-place for as long as people have inhabited the Korean peninsula. Numerous Neolithic remains have been found in the valley. Around the 1st century, the valley is believed to have been inhabited by the Byeonhan confederacy tribes. During the Three Kingdoms period, the Gaya confederacy controlled the valley, until they were overrun by Silla in 562. These states exploited the river's potential for navigation and commerce, operating a thriving trade in armor and weapons with neighboring countries, including Yamato period Japan. Through the Silla, Goryeo, and Joseon periods, the river continued to serve as a major transportation corridor in the Gyeongsang region. It was especially used for transporting fresh seafood inland, such as mackerel, which were salted and dried in order to prevent them from spoiling. The city of Andong was the farthest inland the fish could be brought before going bad, so many people flocked there during the Joseon Dynasty to eat fish. As a barrier to movement, the Nakdonggang River gained sudden prominence during the Korean War. The southern length of the river formed the western portion of the Pusan Perimeter, which the UN forces fought to maintain during the autumn of 1950. The bridge over the Nakdonggang River at Waegwan was blown up on August 3, 1950 in an effort to prevent North Korean forces from advancing on Daegu. A large number of South Korean