Smiling was a job requirement for Donut Dollies, so they had to compartmentalize their own fear and sadness about the war. Many grew close to the men they worked with. Emily Strange, a Donut Dolly who was stationed in the Mekong Delta with the Ninth Infantry Division and Mobile Riverine Force, became friends with a soldier named Michael Stacy. She had become close with Stacy because they both played guitar, and they often strummed folk tunes together. But after he died in a helicopter crash in March 1969, she realized that she needed to put distance between herself and the guys she worked with. So she stopped learning their names, and stopped becoming their friends.

Long after the war, she says she believed that there were probably guys she had encountered whose names went onto the Vietnam Wall. But she would not have to face the pain of knowing for sure. It was Ms. Strange’s job to make lonely, frightened soldiers feel better, and she had to show up and do her job despite the fear and isolation she herself felt. She called it putting on her “Eleanor Rigby” face that she kept in a jar by the door.

Of the military women who served in the war, the majority, about 5,000, did so through the Army Nurse Corps. They were there from the beginning: As the historian Kara Dixon Vuic has shown, the Army began deploying nurses to Saigon in 1956 to train Vietnamese nurses. As the war deepened, they had the double duty of treating the physical wounds of servicemen, and sometimes Vietnamese civilians, and offering an emotional salve to injured and dying troops. Some nurses held men as they cried out for their parents and took their last breaths. They broke the news that a man would never walk or see again. Literally and figuratively, nurses carried wounded servicemen across the threshold from combat to a drastically altered life, or death.

Some nurses wore perfume because it reminded their patients of home. In a military hospital in a war zone, it was at once utterly incongruous and a desperately needed bit of normalcy. Lynda Van Devanter, a nurse whose memoir, “Home Before Morning,” was the inspiration for the television drama “China Beach,” wore ribbons in her hair to uphold the feminine image her patients expected and needed. At the same time, she suppressed her emotions and steeled herself to cope with the mental burden of being soothing and pretty to broken and dying men.

Linda Pugsley was a 22-year-old registered nurse working at Boston City Hospital when she joined the Air Force in 1967. She went through basic training and flight school and was commissioned a second lieutenant. At the time, she had no political feelings about the Vietnam War, but she wanted to help take care of American servicemen who were injured there. She figured she could handle it, with good reason: A weekend shift at Boston City Hospital usually included gunshot and stab wounds, car wrecks and other sorts of bloody trauma.