As the battle for control of the South China Sea heats up, Beijing's struggle to assert its authority over another disputed waterway may prove instructive.
China has been warning planes away from reefs it reclaimed in the South China Sea, and has said it reserves the right to announce an air defense identification zone (ADIZ) over the area. It's expected to boost its military presence after the U.S. last week sailed a warship into the 12-nautical-mile (22-km) zone around China's man-made islands.
But controlling the seas may prove easier for China than controlling the air, according to observers, even after the U.S. incursion and with further patrols expected. The U.S. warship did not venture far inside the 12-mile zone, where China's coast guard is practiced in providing a ring of deterrence.