John Collins, a retired Army colonel and veteran of three wars who founded and led a rollicking national security discussion group that helped inform some of the Pentagon’s most influential thinkers, died Nov. 22 at his home in Alexandria, Va. He was 97.

There was no specific cause of death, said Sean Collins, his son.

Col. Collins enlisted in the Army in 1942 and fought in World War II, the Korean War and in Vietnam, where he served as the senior planner to Gen. William Westmoreland, the commander of U.S. forces. But he was best known in Washington for his achievements after he retired from the Army in 1972.

After he left the Army, Col. Collins worked as a senior specialist in national defense for the Congressional Research Service, where he prepared reports on the U.S. military and national security strategy for members of Congress. There, he coined the “Five SOF Truths,” which remain the guiding principles for the training and employment of Special Operations Forces, said retired Army Col. David Maxwell.

Among Col. Collins’s SOF truths was the maxim that “humans are more important than [military] hardware.” He warned that “Special Operations Forces cannot be mass produced” and emphasized that they could not be recruited and trained quickly in response to an emerging crisis.

But Col. Collins’s greatest contribution to U.S. national security was an online discussion group, called the “Warlord Loop,” which he founded in 1998 at age 77 and oversaw until illness forced him to cede daily management of it when he was 92. Col. Collins came up with the idea for the group in the late 1970s when he was still at the Congressional Research Service but received repeated rejections from his bosses for more than 20 years.

His vision was a discussion group in which the national security thinkers could debate ideas without being bound by the typical bureaucratic restrictions, such as seniority, budgets and the built-in biases of the various military services. In 1998, the emergence of the Internet allowed Col. Collins to start the group on his own without any help from senior national security officials.

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The Warlord Loop’s influence was greatest in the years after the Sept. 11, 2001, terrorist attacks, when it became a place where officials from the Pentagon and State Department and troops serving on the front lines in Iraq and Afghanistan could debate the best approaches to battling insurgencies.

Col. Collins often chose the topics that were discussed on the Warlord Loop, which eventually grew to almost 500 members. He also enforced rules of civility, declaring himself the group’s “judge, juror and executioner.” Unlike the Pentagon, which relied on a strict chain of command, the Warlord Loop gave equal weight to all ideas regardless of the source. Junior officers and enlisted personnel, who had battled through long deployments at distant outposts, could share their experiences and ideas directly with senior officials in the Pentagon.

The eclectic online group also included historians, journalists and anthropologists.

“He had a deep curiosity and respected people’s ideas regardless of age, rank or experience,” said Maxwell, a retired Special Operations colonel.

John Nagl, one of the principal authors of the Army’s ­counterinsurgency doctrine, joined the Warlord Loop shortly after returning from a difficult deployment to Iraq’s Anbar province in 2004. He used the online forum as a place to gather and test ideas as he was helping to write the Army’s new doctrine in 2006 and 2007.

“The Warlord Loop influenced U.S. defense policy in ways that will never fully be understood,” Nagl said in an interview with The Washington Post. “[Col. Collins] made it okay to be a military intellectual” in a military that sometimes sidelined thinkers in favor of fighters.

John Martin Collins was born in Kansas City, Mo., on May 14, 1921. He dropped out of high school two times before enlisting in the Army as a private in 1942 and shipping out to Europe, where he served as an airfield controller.

Back in the United States, Col. Collins graduated in 1949 from what is now the University of Missouri at Kansas City and in 1951 earned a master’s degree in geography from Clark University, in Worcester, Mass. He was an intelligence analyst in Korea in the final days of that war and went on to command a secret 800-man signal battalion that monitored Soviet nuclear detonations from Thule, Greenland.

But Col. Collins’s real passion was military strategy. He headed Westmoreland’s campaign planning group in Vietnam from 1967 to 1968 as the U.S. military, built for big conventional conflicts like World War II, struggled to fight an insurgency in which the enemy did not wear uniforms and hid among the people.

After Vietnam, Col. Collins served as the director of military strategy studies at the National War College at Fort McNair in Washington.

“My father always said that it wasn’t until he was in his 50s when he decided what he wanted to do,” said Sean Collins. “That was when he said he hit high gear.”

Col. Collins’s influence was evident in the many tributes that poured into the Warlord Loop on Friday morning from current and former military officers, some of whom were 50 to 60 years his junior.

Survivors include his wife of 68 years, Gloria “Swift” Demers Collins of Alexandria; a son, Sean Collins of Woodbridge, Va.; and two grandchildren.

Col. Collins’s home in Alexandria was full of knives, swords and books on military strategy that he collected on travels across the world. On his coffee table, he kept a tiger skull that he had brought home from Vietnam.

In person and online, his manner was often courtly and self-deprecating.

Before he died, Col. Collins wrote a final posthumous message that was posted in the Warlord Loop on Friday morning. In it, he attributed much of his success in the military, his career and his personal life to “dumb luck” and his wife.

“I would rapidly return to nowhere without her,” he wrote in his final message.

Col. Collins’s many acolytes had a slightly different take on his achievements, especially the wide-ranging influence of the Warlord Loop. “It was he who made it so valuable,” Nagl said. “And it was he who made it possible.”