In September 1956, Chairman of the Joint Chiefs of Staff Admiral Radford indicated within the U.S. government that the military's intention was to introduce atomic weapons into Korea, which was agreed to by the United States National Security Council and President Eisenhower.

[12] On 10 December 1962, Kim proposed a new military strategy to the Central Committee of the Workers' Party of Korea, with increased emphasis placed on irregular warfare, agitation and propaganda, to be achieved by the end of the current Seven-Year Plan in 1967.

The start of the hostilities can be traced to a speech given by North Korean leader Kim Il-sung on 5 October 1966, at the Workers' Party of Korea Conference, where the status quo of the 1953 Armistice Agreement was challenged.

These units were all highly trained and indoctrinated, skilled in demolitions and small-unit tactics, they would usually operate in small teams of 2–12 men, lightly armed with either PPS submachine guns or AK-47s.

Troops were equipped with M14 rifles rather than M16s, the only available tanks were older gasoline powered M48A2Cs, and there were a total of only 12 UH-1 Huey helicopters in South Korea seriously restricting the ability to hunt and engage infiltrators.

[1]: 11–12  No counter-guerilla units or village militias existed in South Korea in 1966 and infiltrators were variously hunted by the ROK Army, Police and the Korean Central Intelligence Agency with no unified control.

[1]: 30 In 1976, in now-declassified meeting minutes, U.S. Deputy Secretary of Defense William Clements told Henry Kissinger that there had been 200 raids or incursions into North Korea from the south, though not by the U.S.

[1]: 33 Following the first KPA attack on US forces in November 1966, Bonesteel formed a working group to analyse the North Korean strategy and develop a counter-strategy to defeat it.

Beyond the southern boundary or "south tape" of the DMZ, no defensive restrictions applied and a combined U.S.–Korean engineer force constructed an in-depth Barrier comprising a 3m tall chain-link fence, topped by triple strands of concertina wire and reinforced by interwoven saplings and steel engineer pickets, behind it a narrow, raked-sand path paralleled the fence to highlight footprints.

The Barrier could not prevent infiltration (it was estimated that the North Koreans could cut through the fence in 30–40 seconds), rather it was intended to slow movement and provide easy observation.

A new four monthly rotation scheme was introduced in October 1967 to ensure that each Battalion received only its fair share of time manning and patrolling the Barrier.

Along the coasts, some 20,000 unarmed coastwatchers, sometimes supplemented by ROKA reservists, patrolled the beaches and when signs of landings were discovered these would be reported to the National Police and quick reaction forces would be deployed.

Poor communications and a lack of helicopters meant that the quick reaction forces seldom arrived in time before the infiltrators dispersed in the Korean hinterland.

The instruction established a national coordinating council with clear chains of command for all classes of incidents ranging from individual agent sightings to province-level unrest.

The mission of Unit 124, as explained to them by KPA Reconnaissance Bureau chief, Lieutenant General Kim Chung-tae, was "to go to Seoul and cut off the head of Park Chung Hee".

By the morning of 20 January the police and military were on full alert, but not knowing the mission of Unit 124 they were attempting to guard important sites as well as the approaches to Seoul.

[1]: 63 Unit 124 entered Seoul in 2–3-man cells on 20 January, and noting the heightened security and by eavesdropping of ROKA radio frequencies they devised a new assault plan.

Changing into uniforms of the 26th Infantry Division they proceeded to march the last 2 km to the Blue House, posing as a unit returning from a counter-guerilla patrol.

The ROKA, police and U.S. Army began a massive manhunt as the remaining members of Unit 124 attempted to escape north and cross the DMZ.

[1]: 64–65 On 23 January 1968 North Korean patrol boats operating under cover of MiG-21 fighters captured the USS Pueblo (AGER-2) in international waters northeast of Wonsan, killing one crewman.

He regarded the Blue House Raid as having been planned at the highest levels in North Korea, while the seizure of the Pueblo seemed merely opportunistic and the timing of the Tet Offensive as helpful but coincidental.

[1]: 74–75 The Blue House Raid and the Pueblo Incident both served to raise the profile of the low-intensity conflict being fought in South Korea and finally brought in the resources needed to fully implement the joint U.S./ROK counterinsurgency strategy.

Several thousand additional enlisted men were allocated to Eighth Army alleviating manpower shortages while the Imjin Scouts [ko] programme improved training in counterinfiltration tactics.

[1]: 83–84 While the DMZ became increasingly difficult to penetrate during 1968, South Korea's coastline, despite some improvements in ROK Navy capabilities, remained vulnerable to infiltration.

[1]: 82–83 On the night of 30 October 1968, 120 men of Unit 124 landed at eight separate locations between Ulchin and Samcheok in Gangwon province and moved inland on a 30-day mission to create guerilla bases in the Taebaek Mountains.

[23] By the time Park suspended the operation on 26 December 110 North Koreans had been killed and seven captured, for the loss of 40 regular army, police and militia and 23 civilians.

[1]: 86–87 By the end of 1968 it was apparent that despite two years of unconventional operations, North Korea had failed to ignite an insurgency in the South, the U.S.–ROK relationship was stronger than ever and Park had cemented his legitimacy with the population.

[1]: 99 On 15 April 1969 (the birthday of Kim Il-sung), two KPAF MiGs shot down a USAF EC-121M Warning Star on an electronic intelligence mission 167 km off the east coast of North Korea, killing all 31 crewmen.

Isolated incidents continued to occur particularly along the ROKA-controlled sectors of the DMZ, but it had become clear that the North had abandoned its hopes of starting an insurgency in the South.

[24] Several other socialist figureheads, including Leonid Brezhnev, criticized the North Koreans for engaging in escalation as the DMZ conflict could lead the Park regime to further clamp down on opposition and to intensify its military collaboration with the US.