Two Kansans on Knife 13 were among the last casualties of Vietnam. They died on a rescue mission.

When did the Vietnam War end?

For Gregory Hankamer and Robert Weldon it came at 9:30 p.m. Tuesday, May 13, 1975, on a CH-53 helicopter with the call sign Knife 13. The helicopter was part of a massive and hastily organized effort to rescue the crew of the Mayaguez, an American merchant ship seized the day before by the Khmer Rouge in disputed waters off Cambodia.

Knife 13 crashed, killing all 23 aboard.

It was two weeks after the fall of Saigon and a week after President Gerald R. Ford declared, at a speech at Tulane University, that American involvement in Vietnam had ended.

The Mayaguez incident was the bloody and chaotic last chapter of American military involvement in Vietnam. A rushed operation plagued by intelligence failures and bad luck, it serves as a reminder of the heavy price to be paid by those doing the fighting when impractical or even impossible orders are given. Although lauded as a clear military victory with few American casualties at the time, today some of the family members of those killed on Knife 13 question the official account of events.

The Khmer Rouge, the popular name for members of the Communist Party of Kampuchea, had been fighting Vietnamese forces for contested islands in the Gulf of Thailand and harassing merchant ships. On May 12, seven Khmer Rouge soldiers boarded the container ship Mayaguez after shooting a rocket-propelled grenade across its bow and took the 39-member crew captive. The ship’s radio operator managed a desperate SOS.

Alarmed by the prospect of another human and propaganda debacle like the 1968 capture of the spy ship U.S.S. Pueblo, in which North Korea held its crew hostage for 11 months, the White House wanted to resolve the crisis quickly.

“The scheme involved using a force made up of the local 656th Air Force Security Police Squadron (stationed in Thailand),” according to aviation archaeologist Ralph Wetterhahn in his 2001 book, “The Last Battle.” Seventy-five military police volunteers were to be landed atop the cargo containers on the deck of the Mayaguez. Neither the military cops nor the helicopter pilots were trained in such an assault, Wetterhahn noted.

Knife 13 lifted off from Nahkhon Phanom Royal Thai Navy Airfield, one of several CH-53 heavy lift helicopters en route to a staging area at the U.S. base at U-Tapao, Thailand. Officially, the helicopter was on a training mission. On board were 18 military policemen and five crew members.

Sgt. Greg Hankamer, born in Garden City and who had lived as a child with his family in Deerfield, was a 21-year-old Air Force security specialist on Knife 13.

Robert P. Weldon was a flight engineer and part of the helicopter crew.

An Airman First Class, 19-year-old Weldon was a resident of Kansas City, Kansas, and attended Turner High School. The Kansas City Times noted that upon hearing of the death of her son, Mrs. Dean Weldon expressed bitterness toward the United States.

“There’ve been one too many killings over there,” the paper quoted her as saying.

About a month before Knife 13 took off on its rescue mission, Hankamer wrote a letter to the editor of the News-Pilot of San Pedro, California, where his parents were living.

“I believe with all my heart that the people of South Vietnam have suffered much more than any other group of people in history,” Hankamer wrote. “Furthermore, if we can sit back with a clear conscience and watch and listen to hundreds of thousands of free people being killed and suppressed by the Communists” then Americans should be prepared for the fall of the Eastern portion of the world.

Hankamer said he was expressing his personal opinion, and not that of the military or the Air Force, but that many service members and civilians felt the same way he did and did not speak out for fear of “being looked down upon.”

A few minutes into the flight, Knife 13 plunged from the sky and burst into flames on impact with the ground. All 23 passengers and crew perished, along with three military police dogs. Although helicopters were scrambled for a recovery effort, according to Wetterhahn, the intensity of the fire and the exploding munitions aboard Knife 13 dashed hopes of any survivors.

The official cause of the crash was rotor system failure.

Hankamer was due to return to the states but had extended his tour by six months, according to his brother, Luther Hankamer II. There had been a mix-up at the U.S. Embassy in Bangkok with obtaining visas for Greg Hankamer’s wife, Sumalee, a Thai national, and their 1-year-old daughter, Sondra.

Luther Hankamer, a retired Air Force master sergeant who lives in Fort Worth, was stationed at the Royal Thai Air Force Base from 1972 to 1974. Luther told me that when he learned of Greg’s death from an Air Force mortuary officer, he had no idea that his little brother had been on a mission to rescue the crew of the Mayaguez.

“I was more or less in shock when I learned he had been killed,” Luther said. “It hit my whole family hard.”

Luther told me Greg was an easygoing person, somebody who seldom lost his temper, and a talented musician. Greg played the trumpet, just like Luther, and was first chair in high school. When he outgrew his school-issued instrument, Luther gave his brother his own Martin Concertmaster, an instrument Greg brought with him to Thailand.

After the crash of Knife 13, the mission to rescue the Mayaguez crew continued, but was evolving. The plan to deploy Air Force security forces by landing helicopters on the container boxes on the ship was abandoned because Pentagon officials realized the boxes would be crushed beneath the weight of the helicopters, according to Wetterhahn. Also, new intelligence indicated the crew had been removed from the ship and taken to Koh Tang island. Further complicating the crisis was that the U.S. had no diplomatic ties with the Khmer Rouge, which had taken the Cambodian capital of Phnom Pen on April 17, 1975.

The new plan was to retake the Mayaguez and to assault Koh Tang.

The mission was supported by aircraft from the U.S.S. Coral Sea, which had been diverted to the area, and several smaller Navy ships. A brigade-strength amphibious Marine landing force was assembled. As part of the response to the Mayaguez incident, the U.S. also bombed Cambodian ports and targets on the mainland.

On May 15, the assault on Koh Tang began.

But U.S. intelligence had badly underestimated the strength of the Khmer Rouge on Koh Tang, and the Mayaguez crew had already been transferred elsewhere. The container ship was recaptured by U.S. forces. On the island, Marines met a few hundred Khmer Rouge fighters who were already dug in, having prepared to battle the Vietnamese.

The Khmer Rouge shot down four U.S. helicopters and killed 14 Americans during the first assault, according to the national museum of the Air Force. During the fighting, a fishing trawler flying a white flag approached the U.S. destroyer Wilson.

On board the trawler was the entire crew of the Mayaguez, unharmed.

President Ford called an end to the offensive, and reinforcements were moved in to extract more than 230 Marines who had become trapped on the island. The battle that followed was chaotic, confused and filled with horror and heroism. For a detailed account, I refer you to Wetterhahn’s book.

The tragic coda to the Mayaguez incident is that in the confusion a three-man M-60 machine gun crew was left behind on Koh Tang, awaiting a rescue that never came. The loss of the three was in contradiction to Marine Corps doctrine of leaving no one behind. The three were likely captured and executed by the Khmer Rouge. These Marines were Danny Marshall, Gary Lee Hall and Joseph Hargrove.

Lauded as a U.S. victory at the time, the human toll of the operation was at first downplayed. A Pentagon spokesman told the Associated Press there were only a handful of casualties and that no servicemen had been left on the island. The dead aboard Knife 13 also weren’t counted among the casualties and U.S. authorities initially denied the helicopter was involved in the Mayaguez rescue operation. But the truth, eventually, would come out.

In all, 41 Americans died during the Mayaguez incident.

They are the last of the 58,281 names on the Vietnam Veterans Memorial in Washington, which lists American service members killed in chronological order.

Sumalee and Sondra, Greg Hankamer’s wife and daughter, received their visas soon after his death. Luther Hankamer says Sumalee eventually remarried, and both remain in the United States.

“As far as we’re concerned,” Luther said, speaking for himself and Greg’s circle of friends, “it was an unnecessary mission. It was a screw-up on intelligence because the crew of the Mayaguez was already being released when the attack on the island took place to rescue them. And intelligence also said the island was lightly defended, with only company-level strength. When they got there, they found almost a regiment of the Khmer Rouge army.”

He is concerned that the official story about mechanical failure bringing Knife 13 down might not be accurate. He referred me to Jennifer Stelling, the niece of Sgt. Jimmy Black, an Air Force military policeman who died on the helicopter. She’s been researching the crash for years.

“I believe the helicopter was likely shot down rather than suffering a mechanical failure,” Stelling told me. “Several key details support this: the presence of active Communist factions in the area known for targeting U.S. aircraft, intelligence reports noting hostiles nearby, and the unusual fact that a flight surgeon on the scene was immediately issued an M-16 rifle for personal protection — an uncommon measure unless enemy contact was expected.”

In addition, Stelling said, records indicate ongoing enemy ground engagements in the area and the fact that other aircraft had been targeted in similar circumstances. Stelling, who lives in Alabama, said she was born after her uncle’s death but became intrigued by the Knife 13 story.

“These factors collectively suggest a hostile environment where the likelihood of ground fire was significant and cannot be dismissed,” she said.

Luther doesn’t know what became of the trumpet he gave his little brother. It wasn’t among the effects returned to the family.

Luther came home in December 1974.

“I just wish that Greg had been able to be on that freedom bird when I left,” he said.

The Vietnam War did not end when Saigon fell, or when Ford declared it was over, or even when remains of some of the Marine dead from Koh Tang were recovered and buried in 2013 at Arlington National Cemetery. For those like Luther Hankamer, who lost brothers and friends or other loved ones, the war lives on. When Luther talks about his brother, he describes an energetic and enthusiastic young man, and one who remains vibrant in memory. The tragedy of Knife 13 is a wound that is ever fresh.

Greg Hankamer’s body was recovered after the crash and buried in California.

Robert P. Weldon is buried in Alabama.

The gun team left behind on Koh Tang has not officially been recovered. The Defense MIA/POW Accounting Agency lists Hall, Hargrove, and Marshall as “unaccounted for.”

Max McCoy is an award-winning author and journalist. Through its opinion section, the Kansas Reflector works to amplify the voices of people who are affected by public policies or excluded from public debate. Find information, including how to submit your own commentary, here.