Army Brig. Gen. Douglas Kinnard, who was decorated for combat service in Vietnam and later as a college professor conducted a high-profile survey showing that many of his fellow generals thought the war should not have been fought, died ­July 29 at a hospital in Chambersburg, Pa. He was 91.

The cause was pneumonia, said his administrative assistant, Joanne Garland.

Many historians have spoken critically of the U.S. involvement in Vietnam, which cost more than 58,000 American lives, but Gen. Kinnard provided a strikingly atypical voice of dissent against the war. A West Point graduate, he served in World War II, the Korean War and Vietnam before embarking on a second career as an academic.

He was the author of eight books, most notably “The War Managers” (1977), which reported that a large portion of American generals were critical of how the Vietnam War was run. Among other concerns, they said that the enemy casualties were exaggerated to show progress and that U.S. military tactics such as search-and-destroy missions were ineffective.

He based his findings on a questionnaire sent to more than 170 generals who had been assigned to Vietnam between 1965 and 1972, the peak years of U.S. involvement. Gen. Kinnard sought only information based on firsthand knowledge and promised anonymity to any general who responded. More than 100 participated; Gen. Kinnard excluded himself from the survey.

Retired Army Brig. Gen. Douglas Kinnard, who was decorated for combat service in Vietnam and later conducted a high-profile survey showing that many of his fellow generals thought the war should not have been fought, died July 29 at a hospital in Chambersburg, Pa. He was 91. (Courtesy of University of Vermont )

“I never thought there was a military mind in the crude meaning of the word — the notion that military people think like cavemen,” he told the New York Times in 1977. “But I always thought there was a sort of military mind-set. Perhaps there is. But for the group who managed the war, it doesn’t seem to be so.”

His survey, published by the University Press of New England, showed that 53 percent of the responding generals thought the war was not worth the death toll and civil disruption back home or believed that it should have ended at the advisory stage, the Times reported.

After the book’s release, Gen. William C. Westmoreland, who commanded U.S. military operations in the Vietnam War, said he agreed with some of the concerns raised by the officers quoted by Gen. Kinnard. “There was ample reason for us to get involved” in the war, he said. But he added, “We weren’t allowed to win it.”

In 2011, military historian Cecil B. Currey wrote in the Journal of Third World Studies that Gen. Kinnard’s “remarkable book” should resonate with the generals fighting in Iraq and Afghanistan.

“Generals were so deluded they had no idea what they were doing or how to evaluate success in prosecuting the ‘other war’ of winning hearts and minds,” Currey wrote in his review after the book was reissued. “One pathetic general reported that he was pursuing this goal by sending divisional laundry to Vietnamese women to clean. Free fire zones killed hundreds of innocent Vietnamese as did curfews laid on people without watches.”

Douglas Kinnard was born Sept. 13, 1921, in Morristown, N.J., the youngest of eight children. At 4, he was placed in an orphanage by his divorcing parents.

He was later taken in by a family that ran a boarding house in Paterson, N.J., where three sisters whom he came to know as “Aunt Annie, Aunt Fannie and Aunt Rosie” raised him through elementary and secondary school.

He graduated from the U.S. Military Academy at West Point, N.Y., on June 6, 1944, the day that Allied forces landed at Normandy to begin the invasion to liberate France. He served in artillery units in Europe during the final year of World War II and participated in the liberation of Gunskirchen Lager, a concentration camp in Austria.

In 1948, he received a master’s degree in politics from Princeton University. He later was a NATO staff assistant in France and commanded an artillery division in Germany before his first Vietnam assignment. He gradually became disillusioned by Defense Secretary Robert S. McNamara’s demands for quantitative indicators of progress, notably body counts of the Viet Cong.

Gen. Kinnard later recounted in historian Christian Appy’s 2003 book “Patriots: The Vietnam War Remembered From All Sides”: “I overheard a senior general talking to a colonel, an up-and-coming brigade commander. They were discussing the body count, and the colonel said to the general, ‘Well, the VC are getting harder to find.’ And the general said, ‘Well, brigade commanders aren’t.’ ”

Later, when discussing his survey of generals who served in Vietnam, Gen. Kinnard told The Washington Post that “61 percent said the body count was grossly exaggerated, when, in fact, that was the key factor in measuring results in the war.”

In his last military assignment, Gen. Kinnard led a unit planning for the U.S. incursion into Cambodia in the spring of 1970, which triggered massive antiwar protests back in the United States, especially on university campuses.

By the following autumn, he had retired from the Army and was back in college, studying at Princeton for his doctorate. He received the degree in 1973 and went on to teach at the University of Vermont, the University of Oklahoma, the University of Richmond and the Naval War College. Starting in 1984, he also served a stint as the Army’s chief of military history.

His medals included two awards of the Distinguished Service Medal, the Legion of Merit, the Distinguished Flying Cross, two awards of the Bronze Star Medal and four awards of the Air Medal.

Survivors include his wife of 62 years, Wade Tyree Kinnard of Chambersburg, and a son, Frederick Kinnard of New York.

Because of the intense antiwar sentiment on campus when Gen. Kinnard arrived at Princeton, he said he initially planned to keep quiet about his Army service.

But on the first day of classes, someone asked him if he had been present for the campus protests against the Cambodian incursion. “Well, no,” he said. “Actually, I was in Cambodia.”