PAG-ASA ISLAND, West Philippine Sea—The Armed Forces of the Philippines chief of staff, Gen. Gregorio Pio Catapang Jr., looks worried as he surveys the rusted cranes and eroded runway on the tiny island of Pag-asa, now on the front line of a rapidly intensifying construction war in the South China Sea.

Fewer than 48 kilometers away, China’s giant construction cranes glint on the horizon, a sign of the Asian giant’s reef-building frenzy in the disputed Spratly chain that has seen new islands appear seemingly overnight.

As China and fellow rival claimant Vietnam race to pave over reefs and build structures in the strategically important sea, the Philippines stands out as a laggard.

The 356 residents of the remote Philippine-held coral outcrop of Pag-asa (international name: Thitu) fear they will soon be forced out by China’s aggressive land grab, in a conflict fought, so far, with dredgers and cement.

… “As far as I know, there is not much that the Philippines can do,” even if it wins its UN case, said Harry Sa, an American research analyst for the Singapore-based S. Rajaratnam School of International Studies.

“I think China is doing something smart: It is gaining territory without firing a single shot.”