Assaults Along the Korean Demilitarized Zone, 1966-69

North Korea mounted numerous armed attacks directed against U. S.-ROK forces along the Demilitarized Zone (DMZ) in the latter half of the 1960s. With its sustained military operations along the DMZ, North Korea succeeded in diverting U. S.-ROK attention away from Vietnam, straining the U. S.-ROK relationship, and bolstering Kim Il Sung’s position both domestically and internationally.

Attacks and counterattacks

Armed attacks against U. S.-ROK forces

After North Korean leader Kim Il Sung announced in October 1966 that the U. S. forces should be “dispersed to the maximum everywhere and on every front of the world,” guerrilla-type assaults against U. S. and South Korean forces surged. North Korea started to use larger teams and more heavily armed operatives. Between October 15 and 19, 1966, 11 South Korean servicemen were killed in ambush. On October 21, a South Korean truck was attacked in the western DMZ, killing six South Korean soldiers. During the early morning hours of November 2, the last day of the U. S. President Lyndon Johnson’s visit to South Korea, six U. S. and three South Korean soldiers were killed in two separate clashes with North Korean troops south of the DMZ. On one occasion, a Korean People’s Army (KPA) squad attacked an eight-man U. S. patrol with hand grenades and submachine guns, about one kilometer south of the DMZ, killing six Americans and one South Korean soldier serving in the U. S. unit as Korean Augmentation to the U. S. Army (KATUSA). In another simultaneous attack, a KPA squad attacked a South Korean patrol, killing two soldiers. The November 2 attack on the U. S. patrol became a front-page story in the U. S. media, although the story itself did not attract sustained public attention. Between January and November 1966, six U. S. and 30 South Korean soldiers been killed in 40 such incidents.

The emphasis of North Korean assaults along the DMZ since mid-October shifted from intelligence collection and subversion to “harassment.” Before that, North Korean infiltration agents usually wore civilian clothes and rarely engaged in firefights except when challenged by the South Korean military or security services. In mid-October, North Korean infiltration teams started to seek out and attack South Korean forces. An intelligence memorandum produced by the U. S. Central Intelligence Agency (CIA), dated November 8, argued that (a) although there had been a marked increase in North Korean harassment attacks along the DMZ since mid-October, these actions probably did not reflect a decision to engage in wholesale violations of the Armistice Agreement, (b) there was no evidence that the North Koreans intended to open a “second front” in the Vietnam War, and (c) the North Koreans might have heightened tensions along the DMZ to warn the United States and South Korea against further deployment of ROK forces to Vietnam and to demonstrate North Korean support of Hanoi to other Communist states.

North Korea’s official position was that the United States was intensifying military provocations against North Korea and was creating tension on the Korean Peninsula. On November 5, the North Korean Ministry of Foreign Affairs (MFA) stated that “[o]n the occasion of Johnson’s visit to South Korea, the frantic armed provocations by the U. S. imperialist aggressor army and their puppet troops in South Korea” reached the “stage of foolhardiness,” and demanded that the United States “stop hostile provocations against the D. P. R. K. and quit South Korea at once, taking all their murderous weapons.” In June 1967, an MFA official said: “following U. S. President Johnson’s visit to South Korea in October last year various provocations have been staged in a more premeditated way” on the Military Demarcation Line (MDL), warning that a “grave danger of war breaking out again in Korea at any moment” had been created due to the “U. S. imperialists’ schemes for another war.”

North Korean attacks along the DMZ continued in 1967. In February, a U. S. soldier was killed when North Koreans fired upon his nine-man patrol south of the DMZ. In April, 40-60 North Korean soldiers crossed the eastern MDL. In the following six-hour engagement, the U. S.-led United Nations Command (UNC) side used artillery for the first time since the Armistice. It was in the midst of these events that the MFA issued a statement contending that the “ceaseless military provocations of the U. S. imperialist aggressors have increased tension in Korea to a higher pitch and led the situation to an unbearable, grave stage.” On May 22, North Korean intruders exploded satchel charges in the barracks of the U. S. Second Infantry Division in the first incident of the kind since 1953. Two U. S. soldiers were killed, 16 were seriously injured, and two U. S. army barracks south of the DMZ were completely demolished. On July 16, the KPA killed three U. S. soldiers south of the southern boundary of the DMZ.

Faced with the new developments, Gen. Charles Bonesteel III, Commander in Chief of the United Nations Command (CINCUNC), reported in July that:

Actions along DMZ are also continuing with increasing viciousness with more planned, small-scale attacks being made. Firefights are occurring almost every night. A few days ago three more U. S. soldiers were killed. This year’s score along DMZ to date: firefights 69; NKs [North Koreans] 64 KIA [killed in action], 2 captured; ROK/US 35 KIA, (including 6 U. S. KIA), 87 WIA [wounded in action]. Irritating factor is that in last few weeks NK along DMZ are improving their kill ratio.

North Korean attacks on UNC vehicles also increased. On August 10, a truck was attacked south of the southern boundary of the DMZ, killing three South Korean soldiers. On August 22, the KPA attacked a U. S. vehicle carrying straw, killing one soldier and injuring another. Then on August 29, three U. S. soldiers were killed and five were wounded when two U. S. vehicles were destroyed by mines planted by North Koreans.

During this period, there were also clashes in and near the Joint Security Area (JSA) in Panmunjom where the Military Armistice Commission (MAC) meetings were held. On August 28, 1967, North Koreans attacked a U. S. Army Engineer Company working 200 yards northeast of the JSA advance camp, killing two U. S. soldiers and two KATUSAs and injuring 26 others. On September 8, a brief free-for-all, involving some 40 personnel from both sides, began when a KPA guard hit a UNC officer as he tried to take a picture. On November 29, three KPA guards attacked a UNC guard near the MAC conference building. A fist fight ensued but was stopped by Security Officers from both sides. There were also two sabotage attacks on trains near the DMZ in September. Of 114 North Korean infiltrations in 1967, 69 cases involved armed attacks.

In December, Kim Il Sung stated that the present situation required a “more enterprising, more revolutionary” approach to “accomplish the south Korean revolution. . ” This statement was followed a month later, in January 1968, with an attempted guerrilla raid on the Blue House, the South Korean presidential residence, aimed at assassinating South Korean President Park Chung Hee. The same month, a U. S. intelligence-collection vessel – the USS Pueblo – was captured off the North Korean east coast. North Korean attacks in the DMZ continued and even intensified after these incidents.

On January 22, KPA infiltrators attacked a U. S. guard post and wounded three U. S. soldiers. Two days later, two U. S. soldiers were killed by North Korean agents while in a blocking position to trap remnants of a group of North Korean infiltrators who had attempted to assassinate President Park. On January 25, KPA soldiers mounted raids in the DMZ in an area defended by the U. S. Second Division, killing one U. S. and two South Korean servicemen. On the next day, a U. S. soldier was killed by North Korean agents south of the DMZ.

After a temporary pause in February and March, North Korean attacks resumed in April. Interestingly, after the Senior Members meetings with regard to the Pueblo began in February in the MAC in the JSA, incidents in and near the JSA increased, and U. S servicemen became the preferred targets of North Korean assaults. On April 12, 15 KPA guards armed with clubs hit UNC Joint Duty Office personnel who were inspecting the perimeter on the northern edge of the MDL in the JSA. Two days later, North Korean intruders ambushed a UNC JSA security guard truck en route to the JSA, killing two U. S. soldiers and two KATUSAs. On May 2, one KPA security guard knocked down an unarmed UNC guard near a MAC conference room. On August 26, KPA guards dragged a UNC Security Officer off a UNC jeep and attacked him near KPA Guard Post No. 5 in the JSA. On September 2, some 15-20 North Korean workers assaulted U. S. officers in the JSA after they attempted to return a dropped hat to a North Korean guard. Then on December 1, one UNC officer and one enlisted member were attacked and beaten by at least 15 KPA security guards in the JSA.

There were also attacks along the DMZ. On July 20, two U. S. servicemen were killed in two separate incidents near the DMZ. On August 18, the KPA mounted a surprise raid on the U. S. Seventh Division area, killing two U. S. soldiers. On September 27, two U. S. soldiers were killed when North Korean intruders ambushed their jeep south of the MDL. On October 18, a U. S. vehicle was attacked and four were killed.

While attacks in the JSA drastically diminished after the crew of the USS Pueblo was released on December 23, attacks outside the JSA continued. On April 7, 1969, North Korean soldiers fired some 300 rounds in 40 minutes into UNC positions in the central sector of the DMZ. On September 22, North Korean howitzers and recoilless guns opened fire on a ROK Army guard post in the central sector of the DMZ. On October 18, a U. S. vehicle was attacked in daylight in the western DMZ, and four U. S. soldiers were killed.

South Korean counterattacks

Given North Korea’s statements, the attack on November 2, 1966, against a U. S. patrol unit seems to have been related to Johnson’s visit to South Korea. However, it might not have been the only reason for the particular timing. A less known factor was that some 30 South Korean troops had mounted a raid on October 26, a week before the November 2 attack, against North Korea. The South Korean attack team penetrated through the DMZ into North Korean territory to mount the raid, claiming some 30 casualties on the North Korean side. The United States assessed that by attacking American troops on November 2, the North Koreans might have sought to encourage the United States to take measures to prevent any repetition of the South Korean raid across the DMZ.

The South Korean raid caused some tension between the United States and South Korea primarily because it was executed without approval by General Bonesteel, who at that time exercised operational control over South Korean forces. The raid was thus a violation of the command relationship. After the incident, the CINCUNC and the U. S. ambassador to South Korea warned South Korean leaders against any repetition of such incidents.

Violations of the command relationship continued after the December 2 incident, nevertheless. South Korean Defense Minister Kim Sung Eun organized elite anti-infiltration units with 2,400 men under his command and by February 1968 had conducted on average two raids a month against the North. In particular, 11 such raids were mounted between October 26 and December in 1967. Among them was a raid mounted against a KPA division headquarters in November 1967. The headquarters was blown up and the 12-man South Korean strike team returned without any casualties. Most South Korean cabinet members did not know about these activities since the South Korean infiltration units were under the personal control of the Defense Minister and their activities were closely held secrets even within the South Korean government. South Korea had about 200 anti-infiltration troops in each division near the DMZ and was training an additional group. Also, there was one airborne battalion that could be parachuted in for guerrilla activity.

Cyrus Vance, who visited Seoul in February 1968 as a U. S. special presidential envoy, wrote on the possible unilateral military retaliations made by South Korea against North Korea:

If counter-actions by the Republic of Korea resulted in the outbreak of war with North Korea, the lives of some 12,000 American civilians (most of whom are located in the vicinity of Seoul) would be immediately endangered. Similarly, since American aircraft are parked wing to wing on the six ROK airfields and American military forces are deployed along a key portion of the DMZ – to the West and North of Seoul and across two of the most likely attack routes into South Korea – the prospects of American troops becoming immediately involved in combat with North Korean forces are extremely high. The outbreak of war in Korea could thus be ignited either by a serious North Korean incursion into the South or by a South Korean foray into the North.

The United States emphasized the “provocative nature” of the South Korean cross-MDL attacks directed by Defense Minister Kim, and suggested that some of the most serious North Korean incursions into the South in the past might actually have been launched in retaliation for the South Korean raids. The U. S. side also pointed out that there was no evidence that the South Korean raids had had dampening effects on North Korean actions, and refused to commit itself to an “agreed retaliation policy” suggested by the South Koreans that involved “instant, punitive, retaliatory action” against future North Korean violations of the Armistice Agreement. Moreover, Vance warned President Park that were the South Koreans even to consider removing troops from South Vietnam, the United States would pull its forces out of Korea. Defense Minister Kim was replaced by Choi Young Hee on February 28, 1968, shortly after the Vance visit.

The U. S. officials were also concerned that South Korean decision-makers might lose their temper and take irrational actions. They were particularly worried about President Park’s mental condition. This element compounded their concern about the possible unilateral retaliatory actions by the South Koreans. Vance wrote:  

the raid on the Blue House had unfortunate psychologic effects on him. He felt that both he and his country had lost face and his fears for his own safety and that of his family were markedly increased. Compounding this problem has been his heavy drinking. This is not a new development but it may be having cumulative effects. Highly emotional, volatile, frustrated and introspective, Park wanted to obtain from me a pledge for the United States to join his Government in instant, punitive, and retaliatory actions against North Korea in the event of another Blue House raid or comparable attack on some other important South Korean economic, governmental, or military facility. He wanted my assurance of an “automatic” U. S. response in the event of another serious raid against the ROK. I refused to give any such assurances. Park’s views were mirrored by almost every member of his Cabinet, who, while now civilians, are mostly retired colonels and generals.

Although the Vance visit improved U. S.-ROK relations in the short run, Vance was not optimistic about the long-term prospects. Specifically, Vance was concerned that (a) North Korea might try to get South Korea to take some unilateral action to further divide the United States and South Korea, (b) there was an unstable political situation with Park’s mood and attitude, (c) a serious problem could be raised with the possibility of South Korea’s unilateral action, and (d) Park might not “last.” The United States faced a dilemma in helping South Korea. While the help was certainly needed, there was a danger that the U. S. help might encourage the South Koreans to take unilateral, punitive actions, which could result in escalation.


The military actions against the U. S.-ROK forces produced unintended consequences as well. The most apparent and immediate repercussion was the strengthening of the defense in the DMZ. In this regard, particularly important was the North Korean attack on U. S. forces on November 2, 1966. As Daniel Bolger wrote, patrols in the DMZ had by then actually become “rather pro forma affairs.” However, the November 2 attack changed the situation, and the Americans started to pay serious attention to the North Korean infiltrations. As a result, General Bonesteel loosened the rules of engagement in early 1967 and gave the commanders of the I Corps (Group) and the ROK First Army the authority to use artillery and mortar against enemy elements in or south of the DMZ and against KPA units shooting from hostile territory. Furthermore, in July 1968, the UNC changed its rules of engagement and allowed ROK units in the DMZ to counter North Korean intrusions and ambushes at their own discretion. This change was an important departure from the previous arrangement with which military actions taken by ROK units in border clashes were subject to prior approval by the CINCUNC. Following the new rule, South Korean units used significant artillery and mortar fires along the DMZ three times by 1969. In addition, toward the end of 1967, General Bonesteel and President Park produced two documents on combined counter-guerrilla operations – the UNC Counterinfiltration-Guerrilla Concept Requirement Plan and ROK Presidential Instruction No. 18. According to these decisions, the ROK Army introduced infrared night-vision equipment, searchlights, and infrared gun-sights while it strengthened the protection of guard posts and command posts. In addition, the ROK Army replaced wooden fences with iron fences in the DMZ by mid- 1968. At the same time, the UNC developed a four-layer defense – patrols and guard posts in the DMZ, a barrier defense system just south of the southern edge of the DMZ, and mobile quick-reaction forces behind them – against North Korean infiltrations throughout 1967. By July 1968, the chain-link fence and the new barrier system were installed along the entire southern boundary of the DMZ. As a result, the capabilities of the U. S.-ROK forces in dealing with North Korean provocations had improved dramatically by the end of the 1960s.