By the time White House aides woke President Lyndon B. Johnson in the middle of the night on January 23, 1968, it was already too late — the Navy’s intelligence vessel, the USS Pueblo, sent to spy on North Korea, had been seized by the Communist country.

For weeks, the Pueblo coasted, intercepting communication without incident. As part of Cold War reconnaissance, the Navy and the National Security Agency wanted updates on the status of North Korea’s growing military and the Pueblo — a specialized spy ship packed with advanced sensors and encryption equipment — was the right fit for the mission.

But soon, the warnings came. On January 20, a North Korean modified Soviet-style submarine chaser passed within 4,000 yards of the Pueblo, which was about 15 miles southeast of Mayang-Do — North Korea’s most important submarine base. The next day, a pair of fishing trawlers made an aggressive approach within 30 yards of the Pueblo, but they also veered away.

On January 23, however, the USS Pueblo was approached by a North Korean submarine chaser — a small, fast ship designed to find, track and deter, damage or destroy enemy submarines — and was ordered to stand down or be fired upon. According to U.S. reports, the Pueblo was in international waters 16 miles from shore, but the North Koreans insisted the Americans were in their territory. The Pueblo attempted to maneuver away but, as a slow-moving ship, it had no chance of outrunning the chaser.

Immediately, several warning shots were fired and soon three torpedo boats joined the chaser while two MiG fighter jets provided air cover. A fourth torpedo boat and a second submarine chaser appeared a short time later.

The North Koreans opened fire with cannons and machine guns, wounding the American commander and two others.

The Pueblo was severely outmatched in part because of its intelligence mission, but also because its ammunition was stored belowdecks and its machine guns were wrapped to disguise them — nevermind that no one on the ship had been properly trained to use them.

Faced with an inevitable capture, the Americans stalled for time so they could destroy as much of the classified information on board as possible, but a shredder became jammed with the piles of papers shoved into it, and burning the documents in waste baskets filled the cabins with smoke.

One recent declassified NSA report captures exactly how deeply the debacle ran: “Radio contact between Pueblo and the Naval Security Group in Kamiseya, Japan, had been ongoing during the incident. As a result, Seventh Fleet command was fully aware of Pueblo’s situation. Air cover was promised but never arrived. The Fifth Air Force had no aircraft on strip alert, and estimated a two to three-hour delay in launching aircraft. USS Enterprise was located 510 nautical miles (940 km) south of Pueblo, yet its four F-4B aircraft on alert were not equipped for an air-to-surface engagement. Enterprise’s captain estimated that 1.5 hours (90 minutes) were required to get the converted aircraft into the air. By the time President Lyndon B. Johnson was awakened, Pueblo had been captured and any rescue attempt would have been futile.”