In the fall of 1966, things really began to change on the Korean Peninsula.
The armistice agreement that had marked the de facto end of the Korean War in 1953 had created a demilitarized zone between North and South Korea, a buffer area intended to keep the two countries at a remove.
It didn’t always work. In the years since the ceasefire, the DMZ would be home to occasional clashes which served as brief reminders that the two countries were technically still at war. In 1965, North Korean forces killed 20 South Korean soldiers and four in the year before that.
But starting in mid-October, the atmosphere along the DMZ took a dark turn, foreshadowing a bloody end to the decade. North Koreans, often intelligence agents looking to cross the border through the DMZ, had generally avoided U.S. and South Korean patrols so they could slip through unnoticed.
Now, North Korean forces were heavily armed and actively seeking them out. In a five-day period starting on Oct. 13, 1966, North Korean troops carried out five ambush attacks against soldiers from the Republic of Korea.
U.S. president Lyndon Johnson was scheduled to visit South Korea in a few weeks, but the CIA dismissed the idea that the violence was related. A Presidential Daily Brief offered instead that Pyongyang might be looking to test the mettle of a handful of units that Seoul had recently deployed to the DMZ.
Then on Nov. 2, just as Johnson was about to end his trip to South Korea, a North Korean ambush killed six American troops and one South Korean soldier.
The incidents marked the opening salvos in a campaign of subversion and guerrilla warfare that plunged the Korean Peninsula into violence throughout the late 1960s. Kim Il-sung, founder of the Stalinist dynasty that has ruled North Korea since 1948, had decided to send hundreds of commandos and intelligence operatives to the South to recruit disaffected citizens, carry out acts of sabotage, attack U.S. and ROK troops and build the covert infrastructure to foment a communist revolution.
Intelligence analysts at the time offered a range of motives as to why Kim embarked on his guerrilla campaign of the late 1960s. Explanations included a desire to stir up discontent with the dictatorship of South Korean president Park Chung-hee and put pressure on South Korean forces as the country’s military was also fighting Pyongyang’s comrades in Vietnam.
Regardless of the intent, the efforts ultimately failed. Kim and his covert warriors fundamentally misjudged the political climate among South Koreans, whose staunch opposition to communism and North Korea proved a hostile climate for the North’s attempts to sow revolution.
North Korea began expanding the infrastructure for its revolutionary campaign as early as 1965. Interrogations of captured agents revealed that North Korea’s intelligence agencies started ramping up the training of agents that year and including guerrilla warfare instruction in their curriculum. By 1967, Pyongyang’s spy agencies would be able to crank out an estimated 500 agents a year.
There were also overt hints of a shift in policy. Shortly before the mid-October clashes, Kim Il-sung gave a speech to the Korean Worker’s Party in which he promised a more aggressive line towards both the the South and the United States. Kim thundered that the time had come for revolution in the ROK and that it must be achieved by “violent and nonviolent struggles, legal and illegal struggles.”
Kim also called for fellow communists around the world to rise up against the United States, particularly in Vietnam. A victory against America there, he argued, would shatter the “illusion” of American military might.
After November 1966, the DMZ went quiet again. Incidents along in the border traditionally followed a seasonal pattern and so the lull wasn’t altogether surprising. Since 1953, the North had sent intelligence operatives into DMZ.
In general, North Korean infiltration attempts would peak in the fall and then taper off from November through February. Winter brought the added difficulty of snow and stripped the trees and bushes around the border of their leaves, making concealment harder for agents looking to avoid discovery.
When warm weather came, the operations would start up again.
By the summer of 1967, incidents along the DMZ had already spiked dramatically over previous years, with an uptick in North Korean reconnaissance probes on the positions of United Nations Command forces, comprised of American and South Korean forces operating under U.N. auspices.
The CIA reported that there had been some 200 encounters that year, compared with just 44 in 1966.
The campaign of harassment wasn’t just limited to humans. That summer, Time magazine reported that the Korean People’s Army, aware that the ROK used male dogs to search the border for intruders, began patrolling their side with female dogs in heat in a comic attempt at subversion against South Korea’s canine troops.