While much of the world was busy watching Russia swallow Crimea, few realised that an also dangerous territorial tit-for-tat had begun to unfold earlier this month more in the South China Sea.
At Second Thomas Shoal, a handful of Philippine marines have long been stationed and re-provisioned on the rusting deck of the BRP Sierra Madre, a Philippine naval ship half-sunk into the reef in 1999. Ever since, the vessel and the marines have served to embody Manila’s claim of sovereignty over the shoal. More recently, China has tried to raise the salience of its own claim by intensively patrolling the area.
On 9 March 2014, China made a move to end the status quo at the shoal. For the first time in 15 years, Beijing stopped Manila from delivering supplies to the Sierra Madre. The Chinese Coast Guard forced two Philippine ships to turn away. Manila answered the blockade by successfully dropping food and water to the marines by air. It was then up to Manila whether to send in another supply ship or plane, and up to Beijing whether to leave it alone, chase it away, sink it, or shoot it down.
China claims that the Philippine ships were ‘loaded with construction materials’ to build up Manila’s position. Manila says the ships were merely trying to re-provision the marines ‘to improve the conditions there’, not ‘to expand or build permanent structures on the shoal’.
A dozen years ago China and the 10 ASEAN states signed a 2002 Declaration on the Conduct of Parties in the South China Sea, or DOC. The signers undertook ‘to resolve their territorial and jurisdictional disputes by peaceful means, without resorting to the threat or use of force’. China’s threat of force against the Philippine supply ships at Second Thomas Shoal on 9 March violated the DOC.
The long and ongoing record of unilateral Chinese assertions or aggressions in the South and East China Sea no longer leaves room for doubt as to Beijing’s intention. China wants and is trying to achieve dominance over the waters behind what it calls the ‘first island chain’ and land features that fringe the U-shaped line.
The question is not ‘what does China intend?’ The answer — dominance of some kind and degree — is known. The question is ‘what, if anything, is anyone else prepared to do?’ Read more… 
Donald K. Emmerson heads the Southeast Asia Forum in the Shorenstein Asia-Pacific Research Center at Stanford University.
Published on 18 March in http://www.eastasiaforum.org