Nansha indisputable territory

Another key historical moment is the return of Taiwan after World War II. The 1943 Cairo Declaration, co-signed by China, the United States and Britain, says Taiwan and its subsidiary islands occupied by Japan should be returned to China. In the 1945 Potsdam Proclamation, the three countries reiterated the Cairo Declaration, and China took back Taiwan, as well as Xisha and Nansha islands.

In autumn 1946, China sent a fleet to Xisha and Nansha islands. On Nov 24, two warships reached the main island of the Xisha Islands and the Chinese built a monument there. On Dec 12, two other Chinese warships reached the main island of the Nansha Islands and named it Taiping Island.

According to international law, a country can claim sovereignty over an archipelago if it occupies the main island. Therefore, China's sovereignty over Nansha and Xisha islands is not contestable.

Vietnam intruded upon the Nansha Islands in 1956, when the then South Vietnam government sent marine troops to one of the largest reefs of the Nansha Islands. The South Vietnam government declared Nansha Islands as part of its Phuoc Tuy province in 1973, and granted some foreign-funded companies "permission" to explore the waters for oil.

After reunification in 1975, Vietnam took over the reefs previously controlled by South Vietnam and continued to intrude upon other reefs - at least 29 by now. Besides stationing troops and erecting military bases, Vietnam has also built airports and meteorological stations, and set up other facilities on some large reefs.

Vietnam bases its claim over the Nansha Islands mainly on its so-called historical occupation, control and exploration of the islands. But if that is the case, Vietnam would be contradicting itself because it acknowledged China's sovereignty over the islands from the 1950s to the 1970s.

In 1956, Ung Van Khiem, the vice-foreign minister of the Democratic Republic of Vietnam (DRV or North Vietnam), acknowledged that historically the Nansha Islands were a part of Chinese territory when he met with Li Zhimin, China's charge d'affaires in Vietnam. On the same occasion, another high-level Vietnamese official even said that according to Vietnamese sources, China's claim over the islands went back to the Song Dynasty (960-1279).