China has a "nine dotted line" in South China Sea, and within "nine dotted line" are China's sovereign territorial waters and territory. Some people say that nine-dash line drawn in China is unreasonable and is drawn on doorstep of other countries. However, there is nothing reasonable or irrational about territorial issues. Since formation of international law, it has been recognized internationally that whoever first discovers unclaimed land will own it. The rules are set by Western countries, and we are now acting in accordance with this set of international laws.
Before modern times, Asian countries did not have access to international law, so this goes without saying. But in modern times, countries of Southeast Asia have largely become colonies: Philippines has been occupied successively by Spain and United States, Vietnam by France, Indonesia by Portugal and Netherlands, and Singapore by Great Britain. And only one that has not been colonized is Thailand, which is located within Gulf of Thailand. At that time, small islands in South China Sea were uninhabited, according to international law, whoever occupies them first gets first.
However, first to occupy small islands in South China Sea was not China, but France. In 1933 France occupied nine small islands. This incident caused a strong reaction from China, so map subsequently published by China was drawn up to about 9 degrees north latitude, including nine small islands on line, and marked as "Nine small islands in South China Sea" or "Nine islands in Qiongzhou. In 1935, 29th Meeting of Water and Land Map Review Committee of Government of Republic of China decided that territorial map of political region should clearly show islands of Dongsha, Xisha, Nansha and Tuansha, and confirmed Zengmu Beach (now Zengmu Shoal) at 4 degrees north latitude as southernmost tip of China.
Of course, at a time when national power was declining, such behavior can be understood as "opening map." However, something changed later. During World War II, China became an important part of anti-fascist alliance and one of five permanent members of United Nations. Although France is also a permanent member of Security Council, it was destroyed in World War II and has no right to speak in South China Sea. Therefore, China has publicly declared that Dongsha Islands, Xisha Islands, Zhongsha Islands and Nansha Islands belong to China. At that time, no country in world raised objections, and maps of China published by Soviet Union, Japan, France, Germany, and Great Britain also marked "U-shaped line."
City of Sansha
After that, neighboring countries became independent one by one, finding that territorial waters of China were being pulled up to their doorstep, so they were very unhappy and wanted to occupy Chinese islands in South China Sea. And US is also trying to fish in troubled waters, trying to make South China Sea an open sea. Some people say it's unwise to draw South China Sea next to other countries. At this time, we can look at map of Greece.
After First World War, Greece became independent, and also restored its power on map of Thrace. But Greeks want to take back entire Greek territory, that is, to kill Turkey, because western coast of Turkey was once land of Greece, and Greeks once founded twelve city-states here. After that, Greece started a war against Turkey, but Greece eventually failed and did not restore map along coast of Turkey.
However, Greece has been doing quite well since independence. With exception of Turkish coast, rest of islands have mostly recovered, with exception of British occupation of Cyprus. According to statistics, there are 2,500 islands in Aegean Sea, Greece occupies 2,400, and Turkey has only 60 small and miserable islands. Now, although there is a coastline on western coast of Turkey, as soon as it goes out to sea, it enters territorial waters of Greece. Türkiye is dissatisfied with this phenomenon and proposes to give it a new definition. But Greece says 60 islands and coastlines off coast of Turkey once belonged to Greece.
Map of modern Greece
The territory of Greece has approached door of Turkey, which is also internationally recognized. Some people say that it was once land of a Greek city-state, but Greece seems to have been conquered by Rome over 1000 years ago. How can such a long time be used as a basis for ancient times? Greece can beat city-state era, and Turkey can also beat Ottoman era. But South China Sea is different. No matter what era, countries of Southeast Asia never occupied it before World War II. China's nine dotted lines are all drawn correctly, regardless of time or space.