While still in high school, decades before he became US defense secretary, Ashton B. Carter developed a reputation as more than just the smartest guy in the room. Throughout his life, he often seemed to be the brightest person for miles around.
Dr. Carter, who was 68 when he died Monday evening after suffering a heart attack, did calculus problems just to pass the time as a teenager and pored over medieval history books at a university library when he wasn’t participating in high school sports.
Perhaps best known for his groundbreaking decisions as defense secretary to open combat roles to women and end the ban on transgender people serving in the military, Dr. Carter was director of the Belfer Center for Science and International Affairs at the Harvard Kennedy School at the time of his death.
In the early 1990s, before going to Washington, D.C., to become an assistant secretary of defense, he had directed the Center for Science and International Affairs at what was then Harvard’s John F. Kennedy School of Government.
“This loss is so sudden and so devastating,” Douglas Elmendorf, dean of the Kennedy School, wrote in a message to the university community, announcing that Dr. Carter had died.
In a statement, President Biden called Dr. Carter “a man of extraordinary integrity. Honest. Principled. Guided by a strong, steady moral compass and a vision of using his life for public purpose.”
As deputy secretary of defense in the Obama administration, before he assumed the top role, Dr. Carter oversaw changing and challenging budget priorities during the wars in Afghanistan and Iraq.
“As president, I relied on Ash’s strategic counsel as we invested in innovation and a stronger, smarter, more humane and more effective military for the long term,” President Barack Obama said in a statement Tuesday.
US Representative Seth Moulton, a Salem Democrat and a Marine veteran, wrote in an e-mail that “losing Secretary Ash Carter means losing a mentor and a friend; losing someone we admired and enjoyed; losing someone who has done so much for America and yet had much left to give. He set a tremendous example for us to follow, and our country and our planet our better for his life of service.”
As defense secretary during the last two years of Obama’s administration, Dr. Carter said he decided “to admit women to all military specialties without exception. They are 50 percent of the population. We can’t afford to leave off the table half of the population who can, if they’re the ones who have the best qualifications, do the job.”
Of those service members who are transgender, he said in June 2016 that “our mission is to defend this country, and we don’t want barriers unrelated to a person’s qualification to serve preventing us from recruiting or retaining the soldier, sailor, airman, or Marine who can best accomplish the mission.”
He had previously served as assistant secretary of defense for international security policy during the Clinton administration. In the Obama administration, Dr. Carter was undersecretary of defense for acquisition, technology, and logistics, and then deputy secretary of defense before becoming secretary of defense in 2015.
“Ash was a leader on all the major national security issues of our times — from nuclear deterrence to proliferation prevention to missile defense to emerging technology challenges to the fight against Al Qaeda and ISIS,” Biden said.
Dr. Carter was “the quintessential public servant,” said James Mattis, who succeeded him as defense secretary. “He had views on a number of things, but when it came to the defense of the country it was nonpartisan.”
Mattis added that Dr. Carter “could see to the essence of issues. He was brilliant. He could have made a lot more money doing different things, but he believed in the country.”
To a string of increasingly powerful Defense Department jobs, and to his academic positions at Harvard, Dr. Carter brought an uncommon intellectual background.
A medieval history and physics double-major at Yale University, he impressed a Rhodes scholarship screening committee in part by noting that his hobbies included reading electrocardiograms — and he provided an impromptu interpretation of one for a committee member who doubted him.
He landed the scholarship and received a doctorate in theoretical physics from Oxford University.
Even in the upper echelons of the federal government, Dr. Carter stood out for his intellectual agility.
“He cracks jokes that very few people understand,” Leon Panetta, who was then secretary of defense, told the Globe in 2012, when he elevated Dr. Carter to second-in-command at the department.
Years before Dr. Carter was a rising official in the Defense Department, he wrote an influential report for the Office of Technology Assessment, a research branch of Congress, in which he said President Ronald Reagan’s proposed missile defense system, known as the “Star Wars” space-based shield program, was unworkable.
The “prospect that emerging Star Wars’ technologies, when further developed, will provide a perfect or near-perfect defense system … is so remote that it should not serve as the basis of public expectation or national policy,” he wrote.
Those close to Dr. Carter cautioned, however, that his “Star Wars” analysis should not be taken as a sign that he was a dove, any more than his subsequent Defense Department work should suggest he was a hawk. Graham Allison, then-director of the Belfer Center, told the Globe in 2015 that an independent-minded owl was a more appropriate image.
“Ash is basically pragmatic, not an ideologue,” Allison said then. “The way reality works, owls sometimes kill hawks. But I’d say that the owl comes closer to Ash in that he does not have predictable views. He lives on facts and analysis.”
Ashton Baldwin Carter was born in Philadelphia on Sept. 24, 1954. His father, Dr. William Carter, was a psychiatrist and neurologist, and his mother, Anne Baldwin Carter, was an English teacher.
At Abington Senior High School, in a community just north of Philadelphia, he combined his intellectual pursuits with participating in lacrosse, soccer, and wrestling.
After graduating from Oxford with a doctorate, he worked in research, including as a fellow at the Center for International Studies at the Massachusetts Institute of Technology, and taught at Harvard through much of the 1980s.
At the Belfer Center, where he became director in 2017, Dr. Carter “was devoted to our students,” Elmendorf wrote. “He said that one key reason he returned here was his experience at the Defense Department of visiting abroad and being greeted with the salutation ‘Hello Professor Carter’ from his former students.”
In a statement, Dr. Carter’s family said “he believed that his most profound legacy would be the thousands of students he taught with the hope that they would make the world a better and safer place.”
Dr. Carter leaves his wife, Stephanie; his daughter, Ava; his son, William; and two sisters, Cynthia DeFelice and Corinne Green.
His family said funeral arrangements are pending.
In a short autobiographical essay for Harvard, Dr. Carter wrote that as a Yale undergraduate, he “disdained the ‘preppies’ and other privileged students who seemed to regard college as an opportunity to enjoy freedom at long last. I was an intensely serious student, what would probably be called today a ‘grind.’ "
Dr. Carter had always pushed himself intellectually, even in his downtime as a teenager.
“Sometimes you’d find Ash sitting around doing calculus problems to relax in high school, you know, when the rest of us were doing our best to get out of doing calculus,” his sister Cynthia told the Globe in 2015. “I just thought, ‘That’s Ash.’”
Bryan Marquard can be reached at firstname.lastname@example.org.