''That's the mainland, straight in front of you,'' the escort officer said. He pointed through the narrow slit in our well-reinforced bunker, the opening canopied with camouflage netting.
Across the channel, behind an island that was also communist-occupied, stretched the Fukien coast. The island, clad in green with a beautiful white beach, was only 2,000 yards from where we stood. The mainland was perhaps seven miles distant.
A junk with square brown sail glided across our field of vision on the communist side of the channel. Through binoculars I could see a couple of men moving bundles about on the deck. Nothing about the scene suggested anything other than peace.
Yet, according to the escort officer, there is no part of Quemoy Island that is not squarely within the gun sights of communist artillery. The Republic of China, the Taiwan-based government that still claims to be the only legitimate government of all China, maintains a large garrison on Quemoy and Little Quemoy. The garrison's exact size is a military secret. It is kept in a state of instant readiness to repel any communist attack.
Hsu Nai-hsien, who owns the island's largest fish farm, remembers how, as a child in grade school, he had to jump into dugouts to avoid communist shells during the intensive bombardment of Quemoy in 1958. Communist shelling continued until a couple of years ago on odd days, but it was mostly a token affair.
Mr. Hsu's father started the fish farm in 1955 and built it up gradually through the worst days of the bombardment. Today Hsu, who succeeded his father a few years ago, has 20 acres of fish ponds and five acres of fields. It is a family enterprise, with three brothers and three sisters helping Hsu, plus two workers.
''I sell about 500,000 new Taiwan dollars worth (about $12,500) of fish fry every year,'' he said. ''Before, fish farmers here had to go to Taiwan to buy fish fry. Now we produce enough to meet all our local needs.''
Mr. Hsu, who is 37, went to a vocational school in Taiwan and was a television repairman until called home to help out his father. ''I have a good life here,'' he said. ''Even during the shelling things weren't too bad.''
Life on Quemoy has, indeed, improved vastly since this correspondent was last on the island in the mid-1960s. The 50,000 inhabitants live in neat brick farmhouses or city-type apartment buildings. Some of the villages are charming, retaining the traditional sloping-roofed architecture that is becoming rarer on Taiwan.
As on Taiwan itself, bright red taxis and thundering motorcycles are everywhere. Lt. Col. Chen Hua-min, the escort officer, reels off the latest statistics: The island, with an area of 57 square miles, has 225 miles of paved highway, 200 cars, of which 160 are taxis, 300 trucks, 35 buses, and 3,500 motorcycles. It has four power plants, a salt evaporator, and a granite quarry, as well as a porcelain factory and a distillery.
The civilian population lives above-ground. The garrison is housed almost entirely underground, in caves dug out of solid granite. I visited an underground hospital and a huge underground assembly hall, traveling by jeep through miles of tunnels wide enough to accommodate tanks and heavy guns. On the roads soldiers are everywhere - directing traffic, clearing out the underbrush, drilling, or just relaxing. They come to attention and salute smartly every time an officer goes by. This is a young army, almost all Taiwanese draftees, except for officers of field grade and above.
What do the islanders think of the communist mainland, so close geographically, yet so far in every other way? No one seems to want to say much. For years their image of the mainland was that it was a place of great poverty and deprivation, ruled by a cruel totalitarian government.
Their own government is pretty authoritarian, in its way, but the islanders know that their material standard of living is far better than that of the mainland. There does not seem to be any intercourse with the mainland, any of the smuggling and exchange of goods that Taiwanese fishermen carry out with their mainland counterparts.
''This is a security zone, after all,'' said one islander. ''Most of that kind of business (smuggling, and so forth) is carried out by fishermen from the Pescadores (islands in the middle of the Taiwan Strait) or Taiwan itself.'' Beaches are mined and Quemoy fishermen are allowed to fish only on the seaward side of the island.
According to Colonel Chen, there have been 170 defectors who escaped to Quemoy from the mainland this year, mostly fishermen but including one Chinese Communist soldier. Defectors are interrogated and sent on to Taiwan for screening.
Frogmen from Quemoy still claim regularly to infiltrate the mainland, but they are told not to fire on civilians. Their aim, at least as viewed by one Taiwanese who served as a frogman a couple of years ago, is not to create incidents but to hone their own skills and to bring back some proof that they have actually been on the mainland - such as a nameplate or a traffic sign.
Mainland shipping now moves freely in and out of busy Xiamen, which is within sight of Little Quemoy. Under their new policy of economic incentives and the open door, the communists have set up a special economic zone on Xiamen, where foreign investors enjoy tax and customs privileges.
There has been some talk that Taiwan should do the same with Quemoy. But Taiwan has been hostile to all peace overtures coming from the mainland, and the most that it may contemplate regarding Quemoy is to make it somewhat more accessible to overseas Chinese tourists by replacing uncomfortable propeller-driven military transports with civilian jet flights from Taipei to the island, and by improving tourist facilities on the island itself.
There is already a brand-new 35-room underground military guesthouse open to visitors, and this correspondent can vouch that the ''ordinary soldier's lunch'' it serves visitors is far superior to any GI fare he has ever tasted. But then, so is almost any meal served at the simplest restaurant on Taiwan.