The South China Sea is located in the Western Pacific Ocean and it covers approximately 3,700,000 sq km.
Because it is such a large body of water, the South China Sea is bounded by several countries, including China and Taiwan (north), Thailand and Malaysia (west), Indonesia (south) and the Philippines (east).
Due to the underdeveloped transport infrastructure of the adjoining states, the lack of modern roads and railways, the region depends heavily on ship transport, making the South China Sea the second most used sea lane in the world.
Its strategic location means it is a passing point for what is estimated to be a third of the world's maritime shipping, including that of the maritime crude oil trade.
In 2021, as part of the UK Carrier Strike Group 21 (CGS 21), military vessels and aircraft spearheaded by the Royal Navy's HMS Queen Elizabeth aircraft carrier, will transit through the South China Sea.
What are the disputes over the South China Sea?
There are a number of ongoing territorial disputes over the boundaries of the sea and the islands in the South China Sea.
China, Taiwan, Brunei, Indonesia, Malaysia, the Philippines and Vietnam have diplomatic conflicts concerning their interest in the sea and its related archipelagos.
Every country involved in the disputes claims territory beyond the 200 nautical miles Exclusive Economic Zone (EEZ) – the area at sea where the country's specific sovereign powers apply.
The countries' claims are mainly of two natures: historical, like in the case of China, or geological as in the case of Malaysia.
What is China's nine-dash line?
China claims historic rights to most of the South China sea.
The nine-dash line is a demarcation line used by China and Taiwan to demarcate the area of the South China Sea they claim.
The line is shaped like a U, encompassing the Parcel Islands near the Vietnamese coast, down to the Spratly Islands – which are not too far from Malaysia and Brunei – and back up near the coast of the Philippines and through the Luzon Strait, which separates Taiwan from the Philippine island of Luzon.
The nine-dash line is controversial, and it has been challenged by a number of state actors, including the Philippines, the United States and Indonesia.
The dashed line made its first appearance as early as 1947, in a map published by the government of the Republic of China and subsequently used by the Chinese Communist Party.
In the second version, used by the Party in 1949, two dashes disappeared around Vietnam.
However, they still encompassed the various important archipelagos within the South China Sea.
In 2009, China officially submitted a version of the map including the nine-dash line to the United Nations (UN) and claimed sovereignty over the islands in the South China Sea.
The claim was made without any foundation and in direct contrast to the 1982 UN Convention on the Law of the Sea (UNCLOS), according to which nations who have a coast have the right to an Exclusive Economic Zone (EEZ) 200 nautical miles from their shores.
In 2016, an international tribunal in The Hague found that China's claim lacks a legal basis. However, China has since refused to accept the verdict and continued to claim the waters as its own.
Several countries, including the United Kingdom, are among the many who have so far issued statements rejecting Beijing's claims in the South China Sea.
Are there artificial islands in the South China Sea?
Since the 2010s, China has been transforming part of the much-disputed Spratly Islands in the South China Sea into artificial islands.
The Spratly Islands are an archipelago made up of 750 islands, islets, reefs and submerged atolls which is off the coast of the Philippines and Malaysia.
While there are no native islanders occupying the Spratlys, there are a small number of military forces from China, Taiwan, Malaysia, the Philippines and Vietnam.
China has been turning reefs, rocks and atolls into manmade islands that are large enough to host military-ready runways and harbours large enough to host armed vessels.
What is the United States' role in the South China Sea?
The United States has been conducting several Freedom of Navigation Operations (FONOPs) in the South China Sea.
The US Department of Defense aims to demonstrate "its resistance to excessive maritime claims", including those posed by China in the region, under its Freedom of Navigation Program (FNP).
Over the years, tensions between the US and China have ramped up whenever US ships have transited the South China Sea.
Cover image: An aerial view of China-occupied Subi Reef at Spratly Islands in the South China Sea (Picture: Reuters/Alamy Stock Photo).