1895 – 2020
China’s Maritime Disputes
Disputes between China and its neighbors, including the Philippines and Vietnam, in the South China Sea have intensified in recent decades, while the territorial row with Japan over the Senkaku/Diaoyu Islands in the East China Sea dates to the nineteenth century.

April 17, 1895
Sino-Japanese War Ends

The Sino-Japanese war, fought primarily over control of Korea, ends with the signing of the Treaty of Shimonoseki, in which China cedes territories including Formosa (Taiwan) to Japan. The treaty does not mention the Senkaku/Diaoyu Islands [PDF], which were not discussed during negotiations. Beijing maintains that this transfer included the islands, while Tokyo claims that it had owned them since January 1895, when it officially annexed the uninhabited land. This distinction comes into play after World War II, when China says the islands must be returned to Chinese rule as a result of the Cairo and Potsdam declarations, which oblige Japan to renounce claims to all territories seized through war.
Full article: https://www.cfr.org/timeline/chinas-maritime-disputes