David Ferriero, archivist of the United States, holds his dog tag from the Vietnam War during a tour of the “Remembering Vietnam” exhibit at the National Archives. (Ricky Carioti/The Washington Post)

At night, after Navy corpsman David Ferriero finished his clerical duties aboard the hospital ship off Vietnam, he would volunteer to help triage the wounded being helicoptered from the battlefield.

Some had been shot. Others were missing limbs. Some needed treatment right away. Others were dead when they arrived.

It was 1970, and Ferriero was a 25-year-old college dropout from Beverly, Mass., who suffered from seasickness and was a dedicated, if at times inexpert, corpsman.

Today he is the Archivist of the United States and the impetus behind the sweeping new exhibit, "Remembering Vietnam," that opens Friday in the Archives' flagship building in the District.

The free exhibit, which runs through Jan. 6, 2019, includes some of the most striking documents relating to the war:

●A 1944 memo from President Franklin D. Roosevelt stating that Vietnam, formerly ruled by France, should not be returned to the French after World War II.

"France has milked it for one hundred years," Roosevelt wrote. "The people of Indo-China deserve something better than that."

●A 1946 telegram from Vietnamese communist leader Ho Chi Minh to President Harry Truman begging for U.S. support on Vietnamese independence and opposition to the reintroduction of French control. (The CIA withheld it from Truman, Ferriero said.)

●The last page of President Lyndon B. Johnson's stunning 1968 speech announcing that, as a result of the war, he would not run for reelection. "Accordingly," the president concluded, "I shall not seek — and will not accept — the nomination . . . for another term as your President."

He had crossed out "would" and replaced it with "will."

The exhibit also includes on short term loan three Vietnam-era helicopters courtesy of the North Carolina Vietnam Helicopter Pilots Association. The aircraft were installed Monday night on the lawn outside the Archives on Constitution Avenue.

Ferriero, 71, said he wanted the institution to mount a Vietnam exhibit in part because so many of the war's issues remain sensitive and unresolved.

In a long career that took him to big jobs at major universities and libraries, "no one — no one — wanted to talk about it," he said.

"No one asked me any questions," he said. "No one acknowledged it. . . . Never was it the topic of conversation."

Ferriero, in a recent interview in his office, said he also knew that the Archives had "incredible material in the records — photographs and all of the military records, the unit records. We have a lot of stuff."

"And for me it was important to tell the story from both sides," he said.

One fascinating document in the exhibit is a Viet Cong propaganda poster that echoes, from the enemy's point of view, the notorious U.S. obsession with numbers and body counts.

The poster claims, among other things, that the Viet Cong in 1962 and part of 1963 killed 28,108 South Vietnamese and 222 Americans — double the actual figures. "So that inflated body count was happening on both sides," said curator Alice Kamps, who assembled "Remembering Vietnam."

The exhibit includes CIA models of what appear to be an interrogation room and cell in the North Vietnamese prison known as the Hanoi Hilton, which held many American POWs.

There are transcripts of once-secret American helicopter communications as Saigon, the chaotic capital of South Vietnam, was evacuated by the Americans in 1975.

"Bring ur personnel up thru th building," reads one communication. "Do not let them (the South Viets) follow too closely. Use mace if necessary but do not fire on them."

Although the exhibit covers the war from Ho Chi Minh's appearance at the Paris Peace Conference in 1919 to architect Maya Lin's 1981 design for the Vietnam Veterans Memorial, Ferriero's war had a single goal.

"We were all under the impression that the threat of communism was the biggest challenge," he said. "We were all playing a part in protecting us against communism."

Near the end of Ferriero's enlistment, he was shipped to Vietnam as a corpsman in a psychiatric ward.

"There were a lot of what we called at that point 'character disorders' — kids who were having trouble with authority," he said. "Then there were other folks who had more serious psychotic kinds of things . . . awaiting transfer back to the States."

Eventually, he was transferred to the 700-bed hospital ship USS Sanctuary, only to find the "psych" ward had been closed because too many patients had been jumping overboard.

But Ferriero could type, and he became an administrative clerk. After hours, though, he would help sort and treat the wounded who were transported from the battlefield to a kind of emergency room on the ship.

The helicopters came and went. Sometimes one would crash into the ocean. "In my time, no lives were lost," he said.

The ship would spend the day in the harbor at Da Nang, then cruise off the coast at night. Ferriero, who still has his dog tag on his key chain, said the injured included Americans and Vietnamese, soldiers, Marines and civilians.

One case stood out.

He was trying to start an intravenous line in an injured patient and couldn't find a good vein. Each time he failed, he discarded the needle and got a fresh one.

"Kept throwing down these needles," he recalled. "And at one point he just screamed."

"I thought, 'Oh, Jesus, I'm losing him," he said. "This is it."

"It turned out that I had thrown one of those needles down on the gurney and he had rolled over on it," he said.

Ferriero was embarrassed. His patient "wasn't in that great distress," he said, "but I never followed up to see what had happened to him."

One day earlier this week, as Ferriero checked the exhibit, he joked that there was one thing missing: a Zippo cigarette lighter like those carried by many an American serving in Vietnam.

Later, in his office, he produced the one he kept for many years. It was in pristine condition. "USS Sanctuary" was etched in the side, and on the inside of its box was the famous Zippo slogan:

"It works or we fix it free."

This story has been updated.