The Tumen River one of the two rivers that make up the China-North Korea border. It is also one of the two rivers that comes from Mount Paektu, the mountain on the China-North Korea border, and it empties into the Sea of Japan. The river also makes up the Russia-North Korea border. The name comes from the Mongolian word tümen, which means "ten thousand".
Since the easiest way to leave North Korea is through the China-North Korea border, many North Korean defectors have crossed this river to escape North Korea. Some have even escaped into Russia. However, it has become more difficult to escape the country since the government has sent more guards, more electric fences, and more traps on its borders.