China–North Korea border

Two rivers from one mountain

For all but about 20 miles, the border follows the Yalu, flowing west, and the Tumen, flowing east. Both rise near Paektu (Chinese: Baitou or Changbai), a volcano over 2,700 metres high with a crater lake, Heaven Lake, on top.^[1] The mountain is the source of the Korean foundation myth and a symbol of Korean nationalism in both North and South.^[2]

In 1712 the Qing emperor Kangxi sent the envoy Mukedeng to agree the border with Korea’s Chosŏn kingdom. The Korean side insisted on the Yalu and Tumen, Mukedeng climbed the mountain to find the rivers’ sources, and a stele was put up to mark the line.^[2] Which of the many streams on the mountain was the “true” head of the Tumen stayed in dispute for two centuries.^[1][2]

Japan’s deal with China

After the Russo-Japanese War, Korea came under Japanese protection in 1905.^[1] Japan then took up the border question with China, seeing concessions it could win in Manchuria.^[2] The agreement Japan and China signed on 4 September 1909, known in Korea as the Kando (Jiandao) Convention, recognised the Tumen as the boundary and ran the line at its source from the old monument along a stream called the Shihyishwei.^[1] It put Heaven Lake and sixteen of the mountain’s peaks inside China, and in exchange Japan got railway rights in the region.^[2]

Japan annexed Korea in 1910. Agreements in 1911 and 1915 split jurisdiction over a railway bridge on the Yalu and another on the Tumen at the middle of each, but no treaty ever said where the line ran in the rivers, and the islands were never formally allotted.^[1]

“The Governments of Japan and China declare that the River Tumen is recognized as forming the boundary between China and Korea”^[1]

The secret treaty of 1962

In 1961 the two allies were still publishing rival maps. A Chinese magazine placed Paektu and its lake in China’s Jilin province, while a book from Pyongyang drew the line north and west of the mountain, putting the lake in North Korea. The US Geographer recorded the Paektu stretch as disputed; the two sides’ claims there differed by about 600 square miles.^[1]

North Korea insisted on scrapping the 1909 convention, and after several rounds of talks the two sides signed a border treaty on 12 October 1962. Its details were never made public. According to Kwon and Kim, it divided Heaven Lake with a little over half going to North Korea, meaning China gave up nearly 280 km² it had held under the 1909 terms. Kim Il Sung was able to win the concessions while China and the Soviet Union were competing for his support.^[2]

South Korea was not a party. In 1983, 55 of its National Assembly members submitted a resolution declaring all of Heaven Lake Korean territory, and in 2004 its foreign minister, Ban Ki-moon, called the 1909 convention null and void.^[2]

Bridges at Dandong

The main artery between the two countries is the ageing Sino-Korean Friendship Bridge over the Yalu, between Dandong in China and Sinuiju in North Korea.^[3] A New Yalu River Bridge was finished in 2014 at China’s expense, but it stayed closed for more than a decade because North Korea’s customs area and road links were never built. Work resumed in January 2025 with Chinese investment, and in July 2026 satellite images showed it close to completion.^[3]