The plane was nowhere to be found. At 7 a.m. on April 15, 1969, a spy aircraft called Deep Sea 129 left Japan to embark on an intelligence-gathering mission. Almost seven hours later, it was wiped from the radar. Shortly before it disappeared, military officials noticed the approach of two North Korean fighter jets, gaining on the larger, slower aircraft.

Fearing the worst, Navy command sent an emergency message to the highest levels of government, including the White House. Their gravest concern would soon prove true: an American plane had been shot down by the North Koreans. All 31 people aboard were killed.

The downing of the Lockheed EC-121 came at a particularly tense moment in the ever-fraught U.S./North Korea relations. A little more than a year earlier, North Korean naval forces had swarmed the USS Pueblo, killing one of the crew and taking captive the 82 people on board. On the home front, Americans were enraged. In his 1968 campaign, Richard Nixon would even chastise Lyndon Johnson’s weakness with the refrain, “Remember the Pueblo.” And newspaper editorials called for hawkish retaliation. Finally, in December, the 82 men were released from brutal and torturous captivity, putting an end to 11 months of international crisis.

That wasn’t all. On March 15, 1969, a month prior to the shootdown, a North Korean ambush in the demilitarized zone led to the deaths of seven U.S. soldiers. Even so, the possibility of an aerial attack was far from official concern when the crew of the EC-121 took off on April 15. After all, the United States had conducted around 200 aerial reconnaissance missions around North Korean waters in the beginning months of 1969. None had provoked any considerable gesture of antagonism from the North Korean military.

Radar operators onboard a USAF EC-121, like the one shot down by North Korean fighter jets in 1969.

The particular EC-121 that took off from Atsugi, Japan that day was a refurbished version of a Lockheed Super Constellation. Refashioned as a super-spy plane, it carried six tons of electrical equipment, including a large radome on top where it received radar signals, and an antenna on the bottom that intercepted radio waves. Among the 31 on board were linguistics experts in Russian and Korean. To this day, many of the details about the intelligence mission remain secret, though evidence points to a special strategic interest in mapping out North Korea’s radar infrastructure.

The reconnaissance aircraft was slated for an eight-and-a-half-hour flight. The crew took off at 7 a.m., and flew northwest toward the hostile nation. They were instructed to fly two-and-a-half elliptical cycles before landing at a base in South Korea. The aircraft was to fly no closer than 50 miles off the coast, as North Korea claimed international waters began 12 miles from the shoreline.

A EC-121 taking off in the late 1960s. (Wikimedia)

At around 12:30 p.m., as the EC-121 was flying northward on its ellipse, U.S. Navy radar picked up two MiG fighter jets taking off from North Korea. The Soviet-built fighter aircraft were heavily armed and had supersonic capabilities. More than an hour later, at 1:47 p.m., U.S. radar saw the two fighters close in on the spy plane. Within a few minutes, the reconnaissance craft had disappeared entirely from their radar.

A panicked Navy and NSA sent reports suggesting a devastating and unprovoked attack. The message reached the White House around midnight, and President Nixon was made aware of the situation at 7:20 Washington D.C. time.

The White House was as angry as they were surprised by what marked the biggest American loss of life in the region since the Korean War. An incensed Nixon wanted to strike back. Secretary of Defense Melvin Laird and Secretary of State William Rogers advocated for a more cautious approach to the crisis, with Laird even misleading Nixon about the time necessary to mount an aerial counterstrike. National Security adviser Henry Kissinger was the loudest voice in the room to favor militaristic retaliation. “The world will see the lack of a response as proof of America’s moral decay,” Kissinger said. Memory of the Pueblo incident weighed heavily on everyone’s mind as well, an embarrassment inflamed by an alleged comment from the Egyptian president to the King of Jordan: “After all, it isn’t so risky to defy the United States,” he said, “just look at North Korea and the Pueblo.”

The president and his aides spent the next two days considering their options, ranging from a show of naval force, to seizing North Korean assets, to bombing the air base that sent the responsible fighter jets. The pugilistic faction of the White House was angered even further by a triumphant announcement from North Korea that came two hours after the attack, which described the shootdown as a “brilliant battle success” against the “U.S. imperialist aggressor troops.” (Sound familiar?)

The Soviet Union, though enjoying a lucrative trade in arms with North Korea, opposed the country’s reckless killing. In a moment of rare collaboration, the USSR lent ships to the ultimately doomed rescue effort at sea. Two bodies were recovered from the water.

In Congress, hawkish leaders spoke up as well. Chairman of the House Armed Services Committee, Rep. Mendel Rivers, recommended responding with “whatever is necessary,” against North Korea, saying it was time “to give them what they ask for.” He asked, “How long will we let a little insignificant Communist satellite push this nation to the point where we are being laughed at by the rest of the world?” Kissinger proposed a strong counterattack, even if it meant that the U.S. eventually “go nuclear.” Indeed, as the White House debated a course of action, a pilot named Bruce Charles stood by on a South Korean tarmac, awaiting the call to drop a nuclear bomb on the enemy 20 times as powerful as the one that destroyed Hiroshima.

A news conference was planned for April 18, with military retaliation still a possibility. By the time of the conference, however, the Nixon administration decided on a naval show of force (including three aircraft carriers, destroyers, and battleships), and to continue aerial reconnaissance missions undeterred. Many praised the president for refusing to escalate a fruitless conflict, with some critics wondering why the administration would continue these spy missions, when all they might do is invite opportunities for chaos with an unpredictable enemy.

The actual nature of the EC-121 shootdown remains somewhat mysterious, with North Korea’s version consisting mostly of propagandistic boasts (felled “with a single shot”), while many components of the American investigation are still classified. An NSA report released recently, however, posited that the spy plane was felled by one or two aerial missiles of a model copied from a U.S. Sidewinder.

But why the attack happened is still unclear. The efficiency with which the North Korean military mobilized its air force suggests an attack on a U.S. spy plane had been planned for some time. The date of the shootdown warrants attention, as it corresponds with the 57th birthday of North Korean leader Kim Il-Sung, which brought festivals, performances, and revelry nationwide and turned rather seamlessly into a tirade against U.S. imperialists. But in none of North Korea’s missives was a connection drawn to this celebratory day.

Historians have noted that these spontaneous attacks coordinate with a military philosophy voiced by Foreign Minister Pak Seong-Cheol, who argued that periodic and unpredictable assaults on enemy encroachment (whether on land, air, or sea) is what keeps the country safe from massive attack. Two leaders and many decades later, North Korea has in this regard proven itself immensely consistent.