Since demarcation, the DMZ has had numerous cases of incidents and incursions by both sides, although the North Korean government typically never acknowledges direct responsibility for any of these incidents (there are exceptions, such as the axe incident). This was particularly intense during the
Korean DMZ Conflict (1966–1969) when a series of skirmishes along the DMZ resulted in the deaths of 81
American, 299
South Korean and 397
North Korean soldiers. This included the
Blue House Raid in 1968, an attempt to
assassinate South Korean President
Park Chung Hee at the
Blue House. In 1976, in now-declassified meeting minutes, U.S. deputy secretary of defense
William Clements told U.S. secretary of state
Henry Kissinger that there had been 200 raids or incursions into North Korea from the south, though not by the U.S. military. Details of only a few of these incursions have become public, including raids by South Korean forces in 1967 that had sabotaged about 50 North Korean facilities.
Incursion tunnels Since 15 November 1974, South Korea has discovered four tunnels crossing the DMZ that had been dug by North Korea. The orientation of the blasting lines within each tunnel indicated they were dug by North Korea. North Korea claimed that the tunnels were for coal mining; no coal was found in the tunnels, which were dug through granite. Some of the tunnel walls were painted black to give the appearance of
anthracite. The tunnels are believed to have been planned as a military invasion route by North Korea. They run in a north–south direction and do not have branches. Following each discovery, engineering within the tunnels has become progressively more advanced. For example, the third tunnel sloped slightly upwards as it progressed southward, to prevent water stagnation. Today, visitors from the south may visit the second, third and fourth tunnels through guided tours.
First tunnel The first of the tunnels was discovered on 15 November 1974, by a South Korean Army patrol, noticing steam rising from the ground. The initial discovery was met with
automatic fire from North Korean soldiers. Five days later, during a subsequent exploration of this tunnel, US Navy Commander Robert M. Ballinger and
ROK Marine Corps Major Kim Hah-chul were killed in the tunnel by a North Korean explosive device. The blast also wounded five Americans and one South Korean from the United Nations Command. The tunnel, which was about , extended more than beyond the MDL into South Korea. The tunnel was reinforced with concrete slabs and had electric power and lighting. There were weapon storage areas and sleeping areas. A
narrow-gauge railway with carts had also been installed. Estimates based on the tunnel's size suggest it would have allowed considerable numbers of soldiers to pass through it.
Second tunnel The second tunnel was discovered on 19 March 1975. It is of similar length to the first tunnel. It is located between below ground, but is larger than the first, approximately .
Third tunnel The third tunnel was discovered on 17 October 1978. Unlike the previous two, the third tunnel was discovered following a tip from a
North Korean defector. This tunnel is about long and about below ground. Foreign visitors touring the South Korean DMZ may view inside this tunnel using a sloped access shaft.
Fourth tunnel A fourth tunnel was discovered on 3 March 1990, north of
Haean town in the former
Punchbowl battlefield. The tunnel's dimensions are , and it is deep. The method of construction is almost identical in structure to the second and the third tunnels.
Korean wall According to North Korea, between 1977 and 1979, the South Korean and United States authorities constructed a concrete wall along the DMZ. A 2007
Reuters report revealed that there is no coast-to-coast wall located across the DMZ and that the pictures of a "wall" which have been used in North Korean propaganda have merely been pictures of concrete anti-tank barriers. While 800,000 landmines were being removed in 2018, it was shown that the
Joint Security Area along the Korean border was guarded by standard barbed wire. Various organizations, such as the North Korean tour guide company Korea Konsult, claimed a wall was dividing Korea. In December 1999, Chu Chang-jun,
North Korea's ambassador to China, repeated claims that a "wall" divided Korea. He said the south side of the wall is packed with soil, which permits access to the top of the wall and makes it effectively invisible from the south side. He also claimed that it served as a
bridgehead for any northward invasion. The United States and South Korea deny the wall's existence, although they do claim there are
anti-tank barriers along some sections of the DMZ. Dutch journalist and filmmaker
Peter Tetteroo also shot footage of a barrier in 2001 which his North Korean guides said was the Korean Wall. ==North Korean side of the DMZ==