OFFENSIVE PERIMETER: What Beijing is Building in the South China Sea.

The recent addition of mobile equipment for electronic warfare to Mischief Reef adds to the already-extensive electronic network on the reef. To the southeast, China has constructed what is probably a high-frequency, direction-finding antenna array installation which could be used to collect electronic or signals intelligence from transmissions by aircraft or ships in the region, as well as to detect stealth aircraft. North of the island, China has also built what is probably an inter-island communication tower with an associated antenna array similar to the ones found at Cuarteron, Hughes, Johnson South and Gaven reefs. On top of that, China constructed a Doppler very high-frequency omnidirectional range (DVOR) radio system adjacent to the airfield on Mischief Reef. DVOR systems provide short-range navigation information for aircraft without using satellite navigation data.

The deployment of EW equipment is particularly notable because the gear could be used to harass and jam the electronic equipment of various actors in the South China Sea, including the United States. In fact, the equipment deployed to Mischief Reef could have already been used for this purpose. A recent statement from a U.S. Navy pilot, for example, alluded to an incident in recent weeks when his aircraft was likely jammed by Chinese electronic equipment.

China’s next-most vulnerable sea area is the Strait of Malacca, where Beijing has already announced serious interest — so far, merely financial in nature.