From the outside, the rocky hillside at Cuishan looks unremarkable. Step inside, and the silence gives way to an A-shaped underground waterway stretching 357 meters through solid granite — a subterranean harbor once capable of concealing 42 military vessels from enemy artillery fire.
Carved into Kinmen's mountains starting in 1963, the tunnel is one of many surviving remnants of a Cold War defense architecture that transformed the island and its neighbor Matsu into something extraordinary: not the kind of towering protective wall found in the popular anime Attack on Titan, but a territory drilled from within, where the mountain itself became the shield.
The Battle That Put Kinmen on the Front Line
The story of Kinmen's militarization begins in October 1949, when People's Liberation Army forces crossed the water and attempted to seize the island. ROC forces repelled the landing in what became known as the Battle of Guningtou — a victory that cemented Kinmen's symbolic and strategic importance to Taiwan. Evidence of the fighting remains visible today: the exterior walls of the North Mountain Old Western House in Guningtou are still scarred with bullet holes from that battle.
Following the engagement, military deployments to Kinmen deepened and defensive infrastructure began to take shape across the island. Then came the event that would reshape Kinmen from the ground up.
474,000 Shells in 44 Days Drove Kinmen Underground
On August 23, 1958, the PLA launched a massive artillery bombardment of Kinmen, an event Taiwan's historical record calls the "August 23 Artillery Bombardment." Over the main combat phase running from August 23 through October 6, the Ministry of National Defense documented more than 474,000 shells fired at the island. Sporadic shelling continued intermittently for two more decades, until January 1, 1979, when China announced it would cease bombardment.
The strategic lesson was stark: any facility left above ground was a liability. Barracks, ammunition depots, command centers, and naval vessels exposed on the surface risked destruction in the opening hours of a major assault.
Kinmen's geology provided a solution. The island's granite and granite-gneiss rock formations made it possible to hollow out the hills. According to the Kinmen National Park administration, large-scale tunnel excavation began in 1956, with military command, communications, and storage facilities progressively relocated underground on a permanent basis.
The Cuishan Tunnel, completed around 1966 after roughly three years of construction, was the culmination of that logic. What appears from the outside as an ordinary rocky hill conceals an underground dock where boats could maneuver, berth, and conduct resupply operations entirely shielded from observation and attack. If *Attack on Titan* placed its faith in walls built ever higher, Cold War Kinmen chose the opposite direction — not up, but down.
When Villages Became Part of the Defense Grid
The transformation of Kinmen and Matsu extended well beyond military installations. Beginning in 1956, both island groups entered a period of wartime governance — described in official records as a "unified military-civil administration" — in which civilian life was subordinated to military requirements. The arrangement lasted until November 7, 1992.
Qionglin village in Kinmen illustrates how thoroughly the defense logic penetrated everyday life. Designated a "combat village," its residents were enrolled in civil defense organizations, and its neighborhoods were connected by an underground network of combat tunnels. Civil defense personnel were expected to assist with construction and logistics during peacetime, and to take on rescue and defensive duties when called upon.
The defense perimeter, in other words, was not limited to bunkers on the beach. Coastlines, military camps, tunnels, and villages — along with the daily lives of the people inhabiting them — were all woven into a single wartime system.
Matsu Carved Its Wartime Identity Into Rock
The same imperatives shaped Matsu, the other major outlying island group facing China across a narrow stretch of water. Under wartime governance from 1956 onward, Matsu accumulated an overlay of gun emplacements, military strongpoints, underground tunnels, and port facilities that gradually transformed the original fishing village landscape into a wartime geography.
The most dramatic of these is the Beihai Tunnel on Nangan island. In 1968, under what the military designated "Project Beihai," engineers carved underground harbor tunnels into the hillsides of Nangan, Beigan, Xijyu, and Dongyin — allowing landing craft to dock and resupply without exposure to enemy artillery or aerial surveillance.
On the Nangan coastline, another structure takes the concept further still. The Iron Fort, built on a rocky reef jutting into the sea, was not constructed atop the rock but carved into it — tunnels, firing positions, and defensive spaces hollowed directly from a natural outcropping to create a military strongpoint facing open water. Visitors can walk through it today; during the years of active military confrontation, its purpose was coastal surveillance and defense.
A Defense System Hidden in Plain Sight
What remains of this infrastructure across Kinmen and Matsu today constitutes one of the most concentrated collections of Cold War military heritage in Asia. The density of the sites reflects not simply the scale of past troop deployments, but the fact that these islands were systematically restructured according to the logic of the battlefield — hills excavated into command posts, reefs converted into fortresses, villages threaded with underground corridors.
When wartime governance formally ended on November 7, 1992, it closed a chapter that had lasted more than three decades. The tunnels and bunkers it left behind have since become tourist attractions, accessible to visitors who can walk through the same underground passages that once sheltered soldiers, boats, and ammunition from one of the tensest military standoffs in postwar Asia.
The defenses that kept Kinmen and Matsu intact were never visible from the shore. They ran through the rock beneath.
References
- Kinmen National Park Headquarters, Ministry of the Interior — records on military fortifications, battle history, Zhaishan Tunnel, Beishan Old Western House, and Qionglin Combat Village.
- National Development Council Archives Administration — national archives on the 1958 artillery campaign and wartime governance.
- Ministry of National Defense historical research records — artillery statistics for the 1958 campaign.
- Ministry of Culture National Cultural Heritage Database — Matsu wartime cultural landscape materials.
- Tourism Administration, Matsu National Scenic Area — records on Nangan North Sea Tunnel and Iron Fortress.
- National Museum of Taiwan History — records on Kinmen and Matsu wartime governance.
