The last US troops killed in the Vietnam War actually died two years after it ended

Most Americans know the Vietnam Veterans Memorial wall in Washington, D.C, displays the names of every servicemember who died in the war or remain missing in action. But what many may not know is that the last names on the wall were killed in an operation launched two years after the conflict officially ended.

In a hastily thrown together mission to save civilians captured in Cambodia, three Marines were left behind to die at the hands of a Khmer Rouge executioner. And though the mission occurred well after American combat forces withdrew from Vietnam, the names of those Marines were still given their place on the Vietnam Memorial wall.

The 1973 Paris Peace Accords ended U.S. involvement in Vietnam, and two months later the last U.S. combat troops left along with prisoners of war held by the Vietnamese.

But in May, 1975, Communist Khmer Rouge troops from Democratic Kampuchea (modern-day Cambodia), captured an American-flagged merchant ship, the SS Mayaguez, off its coast. And though America was trying to distance itself from the war, President Gerald Ford vowed a response, and historians acknowledge the attempted rescue by U.S. troops as the last official battle of the Vietnam war.

Aerial surveillance showing two Khmer Rough gunboats during the initial seizing of the SS Mayaguez. (U.S. Air Force photo)

Ford ordered the aircraft carrier USS Coral Sea, the destroyer Harold E. Holt, and the guided missile destroyer Henry B. Wilson into the area. He also put the Seventh Air Force and contingents of Marines in the region on alert.

P-3 Orion aircraft dropped flares on the Mayaguez' last known position, which drew small arms fire from the attackers. The Air Force continued to harass the captured ship. So the Khmer troops took the crew prisoner on fishing boats close to the nearby island of Koh Tang.

The Air Force then loaded 75 Security Forces airmen onto five HH-53 Super Jolly Green Giant helicopters and seven Sikorsky CH-53 Sea Stallions to retake the Mayaguez. This plan was aborted when one of the helos, call sign Knife 13, crashed on its way to Thailand, killing all 18 airmen and its five-man crew.

These 23 airmen died en route to the Mayaguez when their HH-53C helicopter crashed due to a mechanical malfunction. (U.S. Air Force photo)

The next plan called for the Air Force to stop all ships between Koh Tang and the Cambodian mainland.

Meanwhile, Marines staged for a simultaneous assault on the Mayaguez and Koh Tang Island. Delta Company of the 1st Battalion, 4th Marines moved to capture the ship, while 600 troops from 2nd Battalion, 9th Marines rescued the crew from the island. The plan called for two helicopters to make a diversionary attack on the eastern beach while the rest of the Marines landed via helicopter on the western side.

Unfortunately, the ship's crew wasn't on Koh Tang; they were on nearby Rong Sang Lem. Koh Tang had 100 defenders who were dug in and armed to the teeth, prepared for an attack from Vietnam, not the United States. And they had enough firepower to give the Marines a real fight.

At 0613 on May 15, the Air Force saturated the decks of the Mayaguez with tear gas as the Holt came alongside. Marines wearing gas masks boarded the vessel in one of the first hostile ship-to-ship takeovers since the Civil War but found the Mayaguez empty.

At the same time, eight helicopters began the assault on Koh Tang and immediately came under heavy automatic weapons and rocket-propelled grenade fire. One of the CH-53s was hit and ignited, killing six Marines, the pilot, and two Navy corpsmen. Three more Marines died from the defending machine guns. The landing troops had to calling in an AC-130 Spectre Gunship to break out of the beachhead.

Just a few minutes before the attack began, the Khmer Rouge Propaganda Minister issued a radio broadcast announcing the release of the Mayaguez crew. The Wilson intercepted the boat carrying the crew and brought them aboard. In the morning in the U.S., President Ford announced the release of the Mayaguez crew to the American public, but not that the Khmer government had released them.

Two hours after the evacuation, a Marine Corps company commander discovered three of his men missing — a machine gun team who protected a helicopter evacuation from the island. The abandoned Marines included Lance Cpl. Joseph N. Hargrove, Pvt. 1^st Class Gary L. Hall, and Pvt. Danny G. Marshall.

Rear Adm. R.T. Coogan would only green light a rescue if the Marines were still alive. The Navy signaled the island in English, French, and Khmer that they wanted to search the island with Cambodian permission if they received a signal.

No signal came.

A picture from an OV-10 over two helicopters shot down on the East Beach of Koh Tang Island (U.S. Air Force photo)

Ten years later, an eyewitness report told the story of Cambodian troops on patrol under fire from an M-16 the very next day. They encircled and captured an American in the incident and were ordered not to discuss the event. That American was Lance Cpl. Hargrove. He was captured and subsequently executed.

One week later, Cambodian troops noticed their food stores were raided at night with strange boot prints left in the mud. They left a trap which captured Hall and Marshall. The two were taken to the mainland and beaten to death with a B-40 rocket launcher, their remains never conclusively found.

A total of 15 men were killed during the Mayaguez rescue mission, with another three missing and presumed dead. That's on top of the 23 airmen lost in the helicopter crash preceding the assault on Koh Tang.

The names of the dead and missing at Koh Tang were the last names to be included on the national Vietnam Veterans Memorial, the wall bearing the names of all Americans killed or missing in the war.