For some time China has been constructing large-scale underground nuclear submarine facilities on its southern island province of Hainan. At the same time, the Chinese People's Liberation Army navy and air force have dramatically reinforced their military structures on the Xisha Islands -- known in the West as the Paracel Islands -- located in the South China Sea off the coast of Vietnam.

The largest military airport in the South China Sea and a super signal and intelligence monitoring station already have been completed on the islands. Recent satellite photos show that the antennas of this intelligence station and related facilities occupy almost the whole of a small island adjacent to Woody Island, where the airport is located. An artificial causeway has been constructed to connect these two islands.

The photos show the smaller island dotted with a mass of radar antennas. Several large vertical high-frequency monitoring antennas are in evidence, which could cover virtually the whole of the South China Sea, all the territory of Vietnam and the Philippines and even high-frequency signals from Malaysia. In addition, there are at least two radar signal detectors and receivers.

Alongside these antennas, four bungalow-shaped structures have been built, apparently used for recording and processing signal intelligence. Judging from the types of antennas deployed on this island, it is clear that they are used for the acquisition of both radio and radar wave intelligence.

The immense scale of these listening facilities suggests that this base is most likely under the jurisdiction of the No. 3 and No. 4 Departments under the People's Liberation Army Headquarters of the General Staff.

The No. 3 Department is responsible for the collection and analysis of wireless intelligence, while the No. 4 Department takes charge of the collection and processing of electronic confrontation and radar wave intelligence. These two departments were established in 1973 after the Fourth Arab-Israeli War, also known as the Yom Kippur War, or the War of Ramadan.

The airport on Woody Island in the Paracels has undergone considerable revamping and reconstruction. Its runway has been extended to 8,200 feet and can handle landings by any of the third-generation combat fighters currently in service in the People's Liberation Army air force, including the Sukhoi Su-30MKK.

A radar navigation station has been built at the airport, plus four large fuel tanks. This means that China's combat aircraft, including the J-8II, J-10A and Sukhoi Su-30MKK, can use this airport as a forward deployment base for refueling while on combat missions. Four aircraft hangars have been newly built, which could be used either for servicing the aircraft when necessary or for the transfer of the fighters. Each of the hangars can accommodate two fighter aircraft.

The naval base on Woody Island also has been upgraded, including the construction of a new anti-wave dike. The length of the dock is more than 1,640 feet, and there are no technical barriers to the anchoring of large-tonnage missile destroyers or frigates.

Facilities on the island are sufficient to accommodate the daily lives of more than 1,000 people. Evidently, this island has become a key comprehensive base of the People's Liberation Army navy and air force for the monitoring of intelligence. It seems that at least one landing craft would come each week to deliver provisions, including all types of fuel and food supplies.

China has territorial disputes in the South China Sea with Vietnam, the Philippines and Malaysia. A military intelligence source from Taiwan claims that since April of this year, Chinese maritime surveillance ships have made frequent appearances in the waters around the Dongsha Islands, also known as the Pratas, which are administered by Taiwan. A Southeast Asian military intelligence source also reported the sighting of at least one Chinese reconnaissance ship in the South China Sea in May.

In the event of a military conflict in the Taiwan Strait, Woody Island could be used by Chinese forces as an unsinkable aircraft carrier and an intelligence station to monitor U.S. navy warships sailing north to support Taiwan.

In the event of a broader regional conflict, the combat radius of the Sukhoi Su-27SKs and Sukhoi Su-30MKKs taking off from Woody Island would allow them to cover the whole of the South China Sea, Brunei, northern Malaysia and Manila in the Philippines.

(Andrei Chang is editor in chief of Kanwa Defense Review Monthly, registered in Toronto.)