Sgt. Maj. Jon Cavaiani is congratulated by President Ford after receiving the Medal of Honor at the White House in 1974. (Frank Johnston/The Washington Post)

Jon R. Cavaiani, an Army sergeant major and Special Forces veteran who received the Medal of Honor, the military’s highest award for valor, for leading his outnumbered unit in the defense of a strategically critical outpost in the Vietnam War, died July 29 in Stanford, Calif. He was 70.

His death was announced by the Congressional Medal of Honor Society. The Web site reported last year that he had myelodysplastic syndrome, a bone marrow disorder.

Sgt. Maj. Cavaiani served in Vietnam in an elite unit of commandos that was deployed on hazardous reconnaissance and counterinsurgency missions, often in enemy-held territory. In 1971, then a staff sergeant, he was serving in a platoon tasked with protecting a remote hilltop in the northwestern reaches of what was then South Vietnam, an area then controlled by the communist North Vietnamese.

Highly advanced — and highly secret — equipment used to intercept hostile communications and monitor enemy movement on the Ho Chi Minh Trail was located on the site, called Hickory Hill.

On June 4 and 5, the camp came under intense enemy fire, including automatic weapons, rocket-propelled grenades and mortar fire. Sgt. Maj. Cavaiani led the defense after his captain was wounded and evacuated.

Sgt. Maj. Cavaiani “acted with complete disregard for his personal safety as he repeatedly exposed himself to heavy enemy fire in order to move about the camp’s perimeter directing the platoon’s fire and rallying the platoon in a desperate fight for survival,” according to his medal citation.

By midday, the onslaught had grown overwhelmingly intense, according to an account in the book “Medal of Honor: Portraits of Valor Beyond the Call of Duty,” by Peter Collier.

Sgt. Maj. Cavaiani directed the helicopters that evacuated U.S. servicemen and indigenous Vietnamese who were fighting with them. But he remained behind.

“That will tell you the most about Jon,” Ralph A. Morgan, a sergeant in the Special Forces who served on Hickory Hill, said in an interview.

“I attribute my life to him,” said Larry Page, a former Special Forces radio operator, who also was evacuated.

A heavy fog gave cover to the North Vietnamese, who launched an intensified ground attack. Sgt. Maj. Cavaiani fought back with small arms and hand grenades and told his remaining men to escape, according to the citation. Some of those who made it to safety believed that he had died.

Severely wounded, Sgt. Maj. Cavaiani took cover in a bunker with a comrade, Sgt. John R. Jones. Together they killed two North Vietnamese who entered. When a grenade exploded in the hideaway, Jones exited the bunker and was mortally shot, according to the account in Collier’s book.

Sgt. Maj. Cavaiani played dead and survived a fire in the bunker before being captured. He was interned in North Vietnamese prisons until his release in 1973.

The following year, he received the Medal of Honor from President Gerald R. Ford. Through his “valiant efforts with complete disregard for his safety,” reads the citation, “the majority of the remaining platoon members were able to escape.”

Jon Robert Lemmons was born Aug. 2, 1943, in Royston, England, to an American father and an English mother. He came to California as a boy and took his stepfather’s surname, Cavaiani, after being adopted by him, said his brother, Carl Cavaiani.

A naturalized U.S. citizen, Sgt. Maj. Cavaiani was initially classified as ineligible for military service because of a severe allergy to bee stings, according to accounts of his life. He joined the Army in his mid-20s after persuading a doctor to attest to his fitness and retired in 1990 as a sergeant major.

Besides the Medal of Honor, his decorations included the Legion of Merit, the Bronze Star Medal and the Purple Heart.

A complete list of survivors could not immediately be confirmed.

After his military retirement, Sgt. Maj. Cavaiani worked in farming and spoke publicly, particularly to students, about his experiences in Vietnam.

“I always tell people I got the medal because I couldn’t outrun them, so I had to fight them,” he told the Modesto Bee of California. “I don’t care to get into the details. I’ve spent too much time trying to forget them.”

Four decades after the battle on Hickory Hill, Sgt. Maj. Cavaiani returned to Vietnam to help Defense Department officials locate the remains of Jones, the sergeant who had remained behind with him and whose body had not been recovered.

Sgt. Maj. Cavaiani remembered and precisely identified the bunker where he and Jones had taken refuge, recalled Page, who also returned to Vietnam to assist in the effort. Jones’s remains were found, and, in 2012, he was buried at Arlington National Cemetery.

“I think you can never repay that debt,” Jones’s brother, James D. Jones, said in an interview. “We say we leave no one behind. In this case, they did not.”

An earlier version of this obituary incorrectly referred to Sgt. John R. Jones as Sgt. James R. Jones. The article has been corrected.