Around half of the world's merchant fleets pass through [this sea] every year carrying an estimated $5 trillion worth of trade.
The area is also believed to contain valuable oil and gas deposits. [T]he Spratly Islands' hydrocarbon deposits [are] valued at $26.3 trillion. [Of course, rights to them are being disputed.]
The latest tension is at the Scarborough Shoal, a small cluster of uninhabitable islands ... [that] has valuable resources including fishing, shipping routes and potentially enormous oil and gas deposits.
After more than two decades of double-digit increases in defense spending, China now has the largest fleet of advanced warships, submarines and long strike aircraft in Asia.