China has quietly, or not quietly if you prefer, been building a strong naval presence in the entire South China sea for a long-long time. This includes building area infrastructure as you have pointed out in mostly international waters.
To me this is part of the long term Chinese strategy to not only dominate the region but to one day, put them in a position to take Taiwan as part of their empire. Taiwan is protected by a treaty with the US. The treaty is basically that the US will step in and prevent a takeover by Red China. I am not confident that the US would step in militarily to stop Chinese aggression, but the administration would likely use sanctions and such.
Last edited: May 13, 2015