evidence: The Yalu and Tumen Rivers, and control of the seas 15Since 1949, China and North Korea have accepted that the course of the Yalu and Tumen rivers constitute the border between the two countries. However, they have refused to situate the demarcation line in the middle of the rivers, adopting the principle of joint ownership, management and use of the two waterways. 16Historically, the main problem has been over the dozens of islands that are to be found in the rivers. China has recognised North Korea’s sovereignty over 80% of these islands, including the biggest ones. Ownership of the islands has been determined by the nationality of their population, but the problem has not been resolved at all for the uninhabited islands, a sort of shared responsibility seeming to apply in their case. Pidan (Chouduandao in Chinese), located at the mouth of the Yalu, was, however, an exception. The island was originally inhabited by mainly Chinese, and while North Korea had control over it, Peking officially regarded it as an integral part of its own territory. The North Koreans then wished to make a gift of it to China in gratitude for its help in 1950-53. In the event, this did not happen, and, in 1963, the Chinese authorities had to evacuate the approximately fifty families who were still living there12.