Ancient Chinese artifacts have been found on these islands and these islands have all been shown on old chinese maps.
Cast aside all your bias and read the history of the Spratly islands, China has been there first.
The French took it from the chinese by force, now the vietnamese claim it for themselves due to supposedly French legacy and due to having it on a map 100 years later
Spratly Islands - Wikipedia, the free encyclopedia
Ancient Chinese maps record the "Thousand Li Stretch of Sands"; Qianli Changsha (千里長沙
and the "Ten-Thousand Li of Stone Pools"; Wanli Shitang (萬里石塘
[7], which China today claims refers to the Spratly Islands. The Wanli Shitang have been explored by the Chinese since the Yuan Dynasty and may have been considered within their national boundaries. [8][9] They are also referenced in the 13th century,[10] followed by the Ming Dynasty.[11] When the Ming Dynasty collapsed, the Qing Dynasty continued to include the territory in maps compiled in 1724,[12] 1755,[13] 1767,[14] 1810,[15] and 1817[16]. A Vietnamese map from 1834 also includes the Spratly Islands clumped in with the Paracels (a common occurrence on maps of that time) labeled as "Wanli Changsha".[17]
According to Hanoi, old Vietnamese maps record Bãi Cát Vàng (Golden Sandbanks, referring to both Paracels and the Spratly Islands) which lay near the Coast of the central Vietnam as early as 1838.[18] In Phủ Biên Tạp Lục (Frontier Chronicles) by the scholar Lê Quý Đôn, Hoàng Sa and Trường Sa were defined as belonging to Quảng Ngãi District. He described it as where sea products and shipwrecked cargoes were available to be collected. Vietnamese text written in the 17th century referenced government-sponsored economic activities during the Lê Dynasty, 200 years earlier. The Vietnamese government conducted several geographical surveys of the islands in the 18th century.[18]