The area is globally important for a few reasons.
Firstly, the South China Sea is a prominent shipping passage with $5.3 trillion worth of trade cruising through its waters every year. That's nearly one-third of all global maritime trade.
Second is what's below the surface: oil and natural gas.
While U.S. estimates have put the amount at 11 billion barrels of oil and 190 trillion cubic feet of natural gas in the South China Sea, one Chinese government-owned oil major actually put the figure closer to 125 billion barrels of oil and 500 trillion cubic feet of natural gas in undiscovered areas.
China claims a wide swath of the waterway based on a boundary first recorded in 1947. The line cited by Beijing reaches as far as 1,200 miles from the south of Mainland China, but it is less than 200 miles away from some coastal areas of Malaysia, the Philippines and Vietnam.
According to international law, every country has the right to claim up to 12 nautical miles from its coast as its territory and can claim an exclusive economic zone extending up to 200 nautical miles for activities like drilling or fishing.
In 2016, an international tribunal ruled against China, saying it has no legal basis for the extensive claims. That decision was legally binding per international law, but there's no enforcement mechanism.
Many in the region welcomed the news, but the Chinese government has ignored the ruling, building more artificial islands and bases.