The issue of the South China Sea at the moment has become a hot issue among the media amid sea disputes between China and some other countries in the region.

My perception is that there were no major incidents occurring in the South China Sea in recent years until the current tensions rose up. The tensions are actually deliberately created by some countries and also have something to do with the involvement of some outside forces.

It needs to be stressed and clarified that there were no territorial disputes at all in the South China Sea before the 1970s. If you look at the maps published by relevant countries at that time, you will find that the South China Sea was shown under Chinese sovereignty.

Relevant countries did not begin to lay claim to islands and sea waters in the area until the discovery of large amount of oil and gas reserves in the South China Sea. The signing of the UN Convention on the Law of the Sea also escalated tensions in the area, but it did not influence the overall peace and stability in the South China Sea.

I think we need to have a better understanding of the relationship between the UN sea treaty and other relevant international laws and regulations. Before the sea treaty came into being, there were already five basic principles of the international law guiding territorial disputes.

According to the first two principles, the country that first discovered and named relevant islands will hold sovereignty over them. Take Huangyan Island for example, which China named as early as in the 13th century.

The third principle is that countries that first developed relevant areas will hold sovereignty over them. The development may happen in many sectors, including fishery and energy resources. Fishermen in China's Guangdong, Fujian and Hainan provinces and the Guangxi Zhuang Autonomous Region have been fishing in the South China Sea for living for generations.

In ancient time, China also established a maritime trade route through the South China Sea. Chinese people used the route to conduct trade with other nations and they also made stopovers in islands at the South China Sea. Such activities can also be seen as a kind of development.

The fourth principle is that the country that first held jurisdiction over relevant islands will hold sovereignty over them. China exercised jurisdiction over the South China Sea in the Song Dynasty (960-1279).

After the World War II, Japan returned to China the Chinese territories it illegally occupied during the war and among them were islands in the South China Sea.

The Chinese government was also the first to dispatch troops to defend islands in the South China Sea.

According to the above-mentioned principles of international law, there should have been no territorial disputes over the South China Sea.

The last major principle in the international law is promissory estoppel, which means you must not withdraw your promises. Vietnam has acknowledged in the past that the Xisha and Nansha Islands belong to China and the Philippines also once acknowledged Huangyan Island as China's territory.

So it is illegal and unreasonable for Vietnam and the Philippines to expand their exclusive economic zone into Chinese territories just because they signed the UN treaty. These acts are a violation of promissory estoppel.

The article was based upon a speech given by Zhu Chenghu, at the World Peace Forum in Beijing. Zhu is director-general and professor at the Academic Department of Strategic Studies of the National Defence University. opinion@globaltimes.com.cn