Up to 40 stretchers an hour were coming off medevac flights — infantrymen, Marines, downed chopper crews injured in a North Vietnamese offensive in late 1968.

Ronald Glasser wanted to help, but he hadn't been in an operating room since medical school. The 29-year-old doctor had been drafted, given the rank of captain and assigned to the small pediatrics unit at a military hospital in Zama, Japan. His job was to treat the children of U.S. military families based in the area.

He met his colonel on a stairwell. Medical teams were struggling with the sheer numbers of casualties. Glasser explained that he may be a bit rusty as a surgeon.

"That's okay, captain," the colonel said, Glasser recalled, "we'll give you the little wounds."

Glasser scrubbed up. And, without knowing it at the time, he was about to begin a journey into the private suffering of war wounded and the toll on those who try — and sometimes fail — to keep them alive. His 1971 book, "365 Days," became part of the canon of firsthand accounts from the Vietnam War for its unblinking narrative on what he witnessed amid the young men whose lives were riven by horrific injuries and mental trauma, and captured at times the violent attitude of many service personnel to the land they were supposed to be fighting for.

"It's not political," said Glasser, who died Aug. 26 at a veterans' hospital in Minneapolis, at 83. "It's just the way it was."

Glasser said he didn't intend to write about his experiences in the military, three years after getting his medical degree from Johns Hopkins University. He opposed the war. He thought he would just ride out his time with the U.S. Army Medical Corps at the hospital in Zama, one of four U.S. field hospitals in Japan's farm belt southwest of Tokyo.

He was stunned, however, at the scope of the grievously injured or mortally wounded arriving from Vietnam. Between 6,000 and 8,000 service members a month were airlifted from battle sites, mine fields and ambush attacks. "I soon realized," he wrote, "that the troopers they were pulling off those medevac choppers were only children themselves" — not much older than his pediatric patients back home.

His book, whose title refers to the year-long tour of duty in Vietnam, mixes the raw pain and fear of the wounded with Glasser's physician's eye for how their bodies were torn apart. Many reviewers took note of Glasser's lean and observational style, placing "365 Days" alongside some of the most searing and honest narratives of war's human cost.

Glasser dedicated the book to Stephen Crane, whose "The Red Badge of Courage" vividly portrays the Civil War battlegrounds.

Michael G. Michaelson, a physician and editor, wrote in a New York Times review, "What is remarkable and even noble about this book is not something new, but some thing old and nearly forgotten: a compassion, that is not restricted by doctrine or polemic but that can encompass the agonies of a Vietnamese peasant or an American career officer; a sensibility that knows not only the murdered … but the murderers."

Nevertheless, some public and school libraries did not keep it in their stacks because of the soldiers' use of profanity — a move that Glasser's defenders found myopic given the fierce antiwar protests and the daily body counts on the evening news. The book also was a finalist for the National Book Award.

"They couldn't say 'golly gee,' and they didn't," Glasser testified at a 1981 federal court hearing in Bangor, Maine, after a school banned the book. "It wasn't enough. [The words] showed their anguish. They don't go home and use that language. They were desperate."

Outside the courthouse, veterans in full combat gear marched in support of the book. (The court in January 1982 ordered the school to return it to the library.)

"In the beginning I talked to the kids just to have something to say and to get them talking. Later I came to realize they were all saying the same things — without quite saying them," he wrote.

"They were worried, every one of them, not about the big things, not about survival, but about how they would explain away their lost legs or the weakness in their right arms," he continued. "Would they embarrass their families? … Would anybody love them when they got back?"

He also wrote in harrowing detail about the injuries — legs shredded, faces burned, fingers mangled — as well as the men who didn't make it.

On one soldier badly injured by a mine blast: "There was not enough skin to close his surgical wounds completely, so his stumps were left open. … Despite antibiotics, his wounds became infected. The fourth night in the ward he tried to kill himself. … On the seventh day his fever hit 106 degrees Fahrenheit; he became unconscious, and seven days following his injuries he expired."

Ronald Joel Glasser was born in Chicago on May 31, 1939, to parents who owned a delicatessen. He graduated from Johns Hopkins University with a bachelor's degree in 1961 and stayed at the university to get a medical degree in 1965, later specializing in pediatric nephrology during a fellowship at the University of Minnesota.

He finished "365 Days" after returning from a two-year deployment at the military hospital. "As for me," he wrote, "my wish is not that I had never been in the Army, but that this book could never have been written."

Glasser wrote other books while working in pediatrics, first as a professor at the University of Minnesota and then in private practice until his retirement in 2016.

"Ward 402" (1973) and "The Body Is the Hero" (1976) analyze limitations in modern medical training to holistically treat patients; the novel "Another War, Another Peace" (1985) follows a doctor during the Vietnam War. In "Broken Bodies, Shattered Minds" (2011), Dr. Glasser looked at the history and advances of military medicine, also advocating for better understanding of post-traumatic stress disorder, or PTSD, among veterans.

At the time, he said PTSD research was particularly important as troops in Afghanistan increasingly faced blasts from improvised explosive devices, or IEDs. "The one great success of medicine in Afghanistan is the realization, and the connection, between traumatic brain injuries, concussive injuries, and PTSD," he told NPR's "All Things Considered."

His 10-year marriage to Janis Amatuzio ended in divorce in 1992. In 2008, he married Joy Itman, who confirmed his death from complications related to dementia. They divorced in 2018, but she remained effectively "his wife and partner," she said.

Survivors include three stepchildren from his second marriage, Rachel, Benjamin and Aaron Silberman.

In "365 Days" Glasser was repeatedly struck by how young conscripts would obey orders and do their duty in the field even though some were deeply against the war. All were just counting the days.

"Strange war," he wrote. "Going for something they didn't believe in or for that matter didn't care about, just to make it 365 days and be done with it."