55 years after sending a hit squad on a deadly raid in Seoul, North Korea has found new ways to threaten South Korea

• In January 1968, North Korean commandos slipped across the border into South Korea.
• They were headed to Seoul on a secret and daring mission to kill South Korea's president.

Just before midnight on January 17, 1968, 31 North Korean special forces soldiers cut through a wire fence along the demilitarized zone and infiltrated South Korea without detection.

The commandos, part of a specially trained force called Unit 124, had one objective: kill South Korean President Park Chung-hee.

Their plan was to covertly make their way to the presidential residence, a 62-acre compound known as the Blue House in Seoul's Jongno district.

Once there, they would bypass the outer checkpoints and then conduct an all-out assault on the main building. A little more than 300 yards from their target, however, everything fell apart.

At a boiling point

Tensions on the Korean Peninsula were approaching a boiling point by January 1968. While the US and South Korean militaries were increasingly focused on the Vietnam War, North Korean dictator Kim Il Sung seemed dead-set on reminding the world that the Korean War had not officially ended.

Violent incidents along the DMZ increased from 42 in 1966 to 360 in 1967 — including at least 100 firefights that killed 63 US and South Korean servicemen and wounded 190 more. (That year, the US military classified Korea as a hostile fire zone, making US troops there eligible for combat medals.)

Infiltrations into South Korea, both across the DMZ and by sea, by North Korean agents and commandos were also increasing. Their primary objective seemed to be setting up guerrilla camps in South Korea's remote highlands.

The infiltrations were largely unsuccessful. Up to 15,000 South Korean police and military personnel were involved in detecting and hunting down the infiltration teams.

By fall 1967, South Korean security forces reported killing 130 infiltrators and capturing 43 more, taking more than 130 casualties of their own in the process.

Around that time, the commandos of Unit 124 — elite troops who had been handpicked by the North Korean military's top brass — were finishing their training in North Korea.

They were trained in infiltration, navigation, hand-to-hand combat, and guerrilla warfare. Their preparations were grueling and dangerous.

They were sent on runs for dozens of miles while carrying as much as 60 pounds of gear in freezing temperatures at high altitudes. Some candidates lost toes or whole feet to frostbite. One member of the unit has said they were trained to dig into graves and hide among the bodies for concealment and that their training was so intense they sometimes shot and stabbed each other.

In the lead-up to the mission, members of Unit 124 practiced assaulting a full-size mock-up of the Blue Palace.

The raid

Each of the 31 commandos carried a submachine gun, a pistol, 320 rounds of ammunition, 14 grenades, and a knife. They wore South Korean military uniforms and carried civilian clothes to blend in if they couldn't avoid crowds.

They traveled at night and slept during the day, covering as much as 7 miles every hour when on the move. Two days into their trek through the mountains, they were discovered by four brothers who were out cutting wood.

Unable to deceive the brothers, the commandos took them captive. They had orders to kill any witnesses, but digging graves in the frozen ground would have been almost impossible. Ultimately, the majority of the unit voted to let them go.

The brothers were given a lecture on the benefits of Communism, promised that their liberation was at hand, and forced to pledge not to inform the authorities.

Unfortunately for the commandos, the brothers immediately told the authorities and the entire country was put on alert. Thousands of South Korean soldiers and police mobilized to locate the infiltrators.

Despite the alarm and several more close calls, the commandos remained undetected and reached the Segeomjeong–Jahamun checkpoint, just over 300 yards from the Blue House, shortly before 10:00 p.m. on January 21.

Wearing their South Korean uniforms, they approached the checkpoint in a double-file line. They were stopped by three policemen who, aware that there were infiltrators in the area, were suspicious.

The police demanded to know what the men had under their coats, which would have revealed that they were carrying Soviet-made weapons unlike those used by the South Koreans or Americans. The commandos instead opened fire, starting a massive shootout.

South Korean soldiers soon arrived in huge numbers along with a tank that the commandos had no weapons to take out. In the chaos, the commandos attacked a passing bus carrying civilians, believing they were arriving soldiers, killing multiple passengers.

Having taken casualties of their own and realizing that their mission was hopeless, the commanding officer ordered the commandos to disengage, scatter, and make for North Korea.

Seoul launched an all-out manhunt. By January 29, all but two of the commandos had been killed or had committed suicide. The South Koreans managed to capture one commando, Kim Shin-jo, while the other, Pak Jae Gyong, escaped to North Korea.

Legacy

During the raid and ensuing manhunt, 68 South Koreans and three American soldiers were killed.

After cooperating with South Korean authorities, Kim Shin-jo was released in 1970 and received South Korean citizenship, which led North Korean officials to execute his parents and siblings. He is still alive today. Pak Jae Gyong, meanwhile, became a four-star general in the North Korean military.

North Korea never acknowledged its involvement in the raid, insisting it was organized by South Koreans, but even North Korea's communist allies had no illusions about Pyongyang's role.

South Korea attempted to organize its own commando squad to kill Kim Il Sung, but the effort backfired and the commandos rose up against their handlers.

The raid was quickly overshadowed by North Korea's seizure of the US spy ship USS Pueblo on January 23, 1968. The ship is still on display in Pyongyang. At the end of January, American attention shifted to Vietnam, where North Vietnamese forces had launched the massive Tet Offensive, which would change American views of the war.

North Korea no longer sends death squads across the DMZ — though it has practiced raids on a replica of the Blue House — but it continues to menace South Korea's leaders.

In 2015, Pyongyang warned that it could turn South Korea into "a sea of fire" if Seoul did not stop activists from sending balloons carrying leaflets into the North.

In December, a North Korean drone flew into a no-fly zone around South Korean President Yoon Suk-yeol's office in Seoul. It was one of five North Korean drones that flew into South Korea, the first to do so in five years.

The drones spent five hours over the South before returning home — an incursion that comes amid a record number of North Korean missile tests meant to show off the growing reach of its expanding arsenal.