In 1933, France asserted its claims from 1887
[45] to the Spratly and Paracel Islands on behalf of its then-colony Vietnam.
[46] It occupied a number of the Spratly Islands, including
Taiping Island, built weather stations on 2 of the islands, and administered them as part of
French Indochina. This occupation was protested by the
Republic of China (ROC) government because France admitted finding Chinese fishermen there when French warships visited 9 of the islands.
[47] In 1935, the ROC government also announced a sovereignty claim on the Spratly Islands.
Japan occupied some of the islands in 1939 during World War II, and it used the islands as a
submarine base for the occupation of Southeast Asia. During the Japanese occupation, these islands were called
Shinnan Shoto (新南諸島), literally the New Southern Islands, and together with the Paracel Islands (西沙群岛), they were put under the governance of the Japanese colonial authority in Taiwan.
Japan occupied the Paracels and the Spratlys from February 1939 to August 1945.
[48]
In November 1946, the ROC sent naval ships to take control of the islands after the
surrender of Japan.
[48] It had chosen the largest and perhaps the only inhabitable island,
Taiping Island, as its base, and it renamed the island under the name of the naval vessel as Taiping. Also following the defeat of Japan at the end of World War II, the ROC re-claimed the entirety of the Spratly Islands (including Taiping Island) after accepting the Japanese surrender of the islands based on the
Cairo and
Potsdam Declarations.[
citation needed] Japan had renounced all claims to the islands in the 1951
San Francisco Peace Treaty together with the Paracels, Pratas and other islands captured from the Chinese, and upon these declarations, the government of the Republic of China reasserted its claim to the islands.
A self confident nation do not go to UN courts for solving its disputes. I agree on this point. But The issue here is contested by 4 nations backed by US and Japan.
US and Japan officially don't support any party , and what Japan has to do there, it is not even in the UN Security Council and has island disputes with every single neighoring country.