The January 1968 capture of the U.S.S. Pueblo during a spy mission in international waters cost the life of one American sailor and began a grueling 11-month imprisonment for the other 82 Americans aboard. While the Pueblo crew was remembered for their bravery and defiance, including holding up their middle fingers when forced to pose in staged propaganda photos and films, the incident is also considered among the most embarrassing incidents in U.S. naval history.

Though the surviving crew finally made it home on Christmas that year, the Pueblo, itself, stayed in North Korea, and has remained there ever since, serving both as a museum display and a symbol of that country’s victory over the United States.

Nearly 15 years after armistice was declared in the Korean War, diplomatic relations between the United States and North Korea remained nonexistent. “Back then there was virtually no communication whatsoever” between the two countries, explains Michael Robinson, a professor emeritus of East Asian Studies and History at Indiana University who specializes in modern Korean history.

It was the height of the Cold War, and the United States, was focused on containing communism, and on the escalating conflict in Vietnam. Meanwhile, North Korea wanted to win back total control of the peninsula, and thought timing was on its side to encourage a rebellion or some other crisis in South Korea. As Robinson puts it: “North Korea figured that we were overextended, and we weren’t going to respond if they attacked or otherwise tried to destabilize the South.”

On January 21, 1968, a group of North Korean commandos fought their way into Seoul in an attempt to assassinate the South Korean president, Park Chung-hee, at his official residence, the Blue House. They failed, but dozens of South Koreans were killed in the firefights. Two days later, on January 23, North Korean patrol vessels and torpedo boats surrounded the USS Pueblo, which had been steaming through international waters off North Korea’s eastern coast, listening in on the nation’s communications.

A former environmental research ship that had been converted into a spy ship, the Pueblo was armed with only two machine guns when the North Koreans opened fire. Ten sailors were wounded, one fatally, and after repeatedly radioing for help, the Pueblo’s commander, Lloyd “Pete” Bucher, made the decision to surrender his ship. The North Koreans boarded the Pueblo and had it towed into the eastern port city of Wonsan, taking the remaining 82 Americans aboard (including two civilian oceanographers) as prisoners.

The Pueblo’s sailors were able to burn much of the classified information on board before their capture, but a National Security Agency report (declassified in 2012) stated that the loss “would dwarf anything in previous U.S. cryptologic history.” This was also the first hijacking of a U.S. Navy vessel since the Civil War, and it occurred at exactly the wrong time for the United States. “The Tet Offensive happens January 30, so you can see that the United States is completely unable to really respond to this,” Robinson says. “All sorts of hell was breaking loose. And [President Lyndon B.] Johnson is politically very weak at this point.”

In considering retaliation for the Pueblo’s seizure, the Johnson administration weighed options including a naval blockade of North Korean ports, air strikes on military targets, a ground attack across the Demilitarized Zone separating North from South Korea or even the use of a nuclear weapon. In the end, however, Johnson decided against military action, instead making a “show of force” by ordering hundreds of combat planes and 25 warships to the Sea of Japan near South Korea.

“I think they might have [struck back] if they had been in a different military posture,” Robinson speculates. “They might have tried something more serious. But frankly, I think they were worried about getting the people back from the Pueblo.”

Bucher and the rest of the Pueblo’s crew spent a harrowing 11 months in captivity, during which they were tortured, forced to sign confessions and subjected to relentless propaganda by their captors. At first they resisted, famously raising their middle fingers at the camera and telling the North Koreans it was the “Hawaiian good-luck sign.” Once the North Koreans learned the truth, they punished the prisoners with beatings, cold temperatures and sleep deprivation, according to a lawsuit some of the Pueblo’s crew would later file against the North Korean government.

After protracted negotiations, the United States apologized for spying, and on December 23, 1968, the men were allowed to cross the DMZ into South Korea, carrying the body of Duane Hodges, who had died of wounds sustained in the attack on the ship. They flew back to the United States on Christmas Eve, malnourished and scarred by the torture they had endured.

Though it is still an officially commissioned U.S. Navy ship, the USS Pueblo sits today in the Victorious War Museum in Pyongyang, the North Korean capital. “It’s a hostage,” Robinson says, but it is also a tourist attraction and propaganda tool, a symbol of North Korea’s defeat of an enemy it had despised since the Korean War.

Ahead of President Trump and Kim Jong Un’s meeting in Singapore on June 11, 2018, some called for the return of the Pueblo to make it onto the agenda, though the ship’s fate was among many other weighty topics as nuclear weapons and disarmament and the possible repatriation of the remains of U.S. troops killed during the Korean War. As one former Pueblo seaman and POW, Tom Massie, told the New York Post of the captured ship on which he and his comrades began their long and painful ordeal, “I would like to see it returned because it is a part of our history.”