The Two Koreas_ A Contemporary History - Don Oberdorfer [34]
An important break came in September 1974, when a North Korean Workers Party functionary from the city of Kaesong, just north of the DMZ, defected, bringing with him valuable knowledge and diagrams of some tunnel locations beneath the southern lines. The defector, Kim Pu Song, said that extensive tunnel digging had been ordered from the highest echelons of the party in late 1972, not long after the North-South joint statement in which the two sides agreed to work for peaceful unification and "not to undertake armed provocations against one another, whether on a large or small scale."
According to the defector, the tunnel digging was highly organized, with North Korean army teams of about twelve members each working in shifts around the clock, augmented by supervisors, engineers, technicians, and guards. The defector said that the wartime purpose of the tunnels would be to infiltrate light infantry and special forces personnel into the South to participate in a lightning attack; in peacetime the tunnels were intended to facilitate the infiltration of North Korean agents.
Based on Kim's information as well as its own estimates, the South Korean Command projected the existence of fifteen tunnels under the DMZ. Later the U.S. Command increased the number of actual or suspected tunnel locations to twenty-two.
Even after the defector's information, it took the accident of the steam rising in tall grass to locate the precise location of the first intercepted tunnel in November 1974. In February 1975 the second tunnel was found by extensive exploratory drilling at a suspect site and confirmed by lowering a specially developed camera into a tiny borehole. At the time of its discovery, the tunnel had progressed three-fourths of a mile into the South Korean side of the DMZ. Aerial photography eventually identified its starting point at the base of a mountain nearly three-fourths of a mile into North Korean territory.
Tunnel number two, as it was called, was an extraordinary engineering feat, even bigger and longer than the first one, constructed through solid granite more than fifty yards below ground using modem drilling machinery that had been imported from abroad. Several months after it was found, I made my way down the steep-sloped intercept passage to inspect this impressive construction, accompanied by an American explosive ordnance team and South Korean troops. The floor and ceiling were uneven, but my six-foot frame was able to stand erect at most points along the two hundred yards where I was permitted to go. I could stretch both arms toward the sides of the chamber without touching them. The U.S. Command estimated that the dark, dank chamber could accommodate about 8,000 troops and put through another 10,000 men per hour with light artillery and other supporting weapons. Its intended discharge point would have been well behind South Korean forward defense lines.
Outside the tunnel, I saw South Korean soldiers digging new lines of trenches and bunkers at the approaches to the DMZ to protect themselves against North Korean troops who might pour out of underground structures. The most suprising thing was that, despite the discovery of two tunnels, formal U.S. and ROK protests, and much publicity, the sounds of digging continued to be detected under the surface of the DMZ. All indications were that Kim Il Sung had authorized the digging, and nobody else could give an order to stop.
The U.S. Command and the ROK military responded to the underground challenge by making increasingly sophisticated efforts to locate tunnels far below the surface. In addition to the borehole cameras, the largely secret detection efforts utilized standard and experimental seismic listening devices, complete with soundproof booths for analyzing tapes. Eventually a total of 245 such devices were placed along the DMZ to record underground activity at suspect sites; the tapes were picked up at least once a week for examination.