Last year, he was the country’s top military officer. Now, he is retired on the South Shore

“If the US doesn’t lead in developing those structures that can advance our diplomatic, our economic, our intelligence, and our security interests, somebody else will lead in doing that,'' said retired General Joseph Dunford.John Tlumacki/Globe Staff

Joe Dunford wore the Marine Corps uniform for 42 years, but the retired four-star general has swapped the battle space in Afghanistan and Iraq, as well as political skirmishes in Washington, for a South Shore home a block from the ocean.

He and his wife attend Sunday Mass from their car as protection during the pandemic, and Dunford laughs as he says that he checks the Sharktivity app to monitor the location of any Great Whites patrolling the beaches.

The change is as dramatic as they come.

Last year, Dunford was chairman of the Joint Chiefs of Staff, the country’s highest-ranking military officer, amid the turmoil of the Trump administration. Today, the 64-year-old native of South Boston and Quincy is adjusting to civilian life for the first time since college, a trim man sitting on his outdoor deck in an open-neck shirt and smiling at how once again — in what must seem like forever — he can get a good night’s sleep.

“I’m pretty happy, and my wife is happy that I’m not underfoot,” said Dunford, a graduate of Boston College High School and St. Michael’s College in Vermont. “We always wanted to come back home, and we’ve just kind of blended into the scenery.”

Dunford and his wife, Ellyn, have three children, and he checks in regularly on his mother and father, a Marine veteran of the Korean War who served 40 years with the Boston police and rose to deputy superintendent. Still, blending into the scenery has a different meaning for Dunford than it does for most retirees.

He’s a senior fellow at the Belfer Center for Science and International Affairs at Harvard University, where he mentors national security and intelligence professionals. He works with several nonprofit organizations, including as chairman of Semper Fi & America’s Fund, which provides lifetime support to combat-wounded members of the US military and their families.

Dunford sits on the boards of Lockheed Martin and a private-equity company in New York. And he is co-chair of a congressionally funded, bipartisan study group on the future of Afghanistan, where he served as commander of US forces and the international security coalition in 2013 and 2014.

“I still feel productive. I started getting engaged right away,” Dunford said. “I really miss the people, but what I appreciate is to have a little more balance in my life.”

During a lengthy interview at his home, whose location he requested the Globe not identify for privacy purposes, Dunford spoke in detail about the challenges facing the military, the US role in a changing geopolitical landscape, and the growing military threat posed by China and Russia.

But Dunford did not wish to discuss his personal or professional feelings about President Trump, whom he advised during much of his tenure as Joint Chiefs chairman from 2015 to 2019. He also declined to comment on Trump’s reported disparagement of slain US service members as “losers” and “suckers,” characterizations the president has denied making.

Dunford said his philosophy is to “behave in public the same way I did while on active duty. ... I feel I should not engage in any partisan politics.”

The implications of any public comment on the president and his administration, he said, could complicate the job of Army General Mark Milley, his successor as Joint Chiefs chair and another Massachusetts native.

“I’ve got to let the chairman be the chairman, and there can be only one chairman,” Dunford said.

After a pause, he smiled and repeated a quote from Army General Omar Bradley, a hero of World War II: “The best service a retired general can perform is to turn in his tongue along with his suit and to mothball his opinions.”

Although Dunford did not comment directly on national politics, the worldview he expressed differs significantly from the America First agenda the Trump White House has espoused.

To Dunford, the international institutions and agreements that followed the devastation of World War II — the United Nations, NATO, and the Bretton Woods economic agreement prominent among them — provided a durable framework for global stability that strong US leadership has helped maintain.

“And while some believe that there needs to be some changes in the world order, what I would argue is that we had a vision for what a world order ought to be after World War II,” he said.

“That structure, that order, if you will, brought about peace and security for a long period of time,” he added.

“The president is doing it his way. I’m not going to, as a military leader, comment on how the president is approaching it. But I would argue that the value of these relationships is as critical in the future as it has been in the past.”

A weakening of US leadership and its alliances would have profound global consequences, he said.

“If the US doesn’t lead in developing those structures that can advance our diplomatic, our economic, our intelligence, and our security interests, somebody else will lead in doing that, and there are really only two candidates right now that would step up to take a leadership role in that regard,” Dunford said.

“One is Russia and the other is China. And so the question I would ask is, which of those two countries do you think ought to be helping to establish the international laws, norms, and standards of the future?”

Dunford described China as “the most formidable adversary we will face” in the years ahead, an emboldened military power that is increasingly aggressive in the South China Sea and exhibiting a “might makes right” mindset.

“We shouldn’t look at this as an inevitable cold war. That’s not the picture I’m painting,” he said. “But what I do believe is that our military capabilities and our ability to demonstrate our alliance commitments will certainly be deterring to China in the region.”

China’s confidence and aggressiveness, particularly considering US and Chinese forces often operate in close proximity, “can result in a dangerous miscalculation, and I think that’s what most leaders are concerned about now ― more a miscalculation than a conscious decision to go to war,” Dunford said.

“You could easily drift into a crisis that could lead to a conflict, and we ought to be doing all we can do to mitigate that risk,” he said.

Dunford checked off a long list of other concerns, including Russia’s continued interference in US elections, the assumption that North Korea has an intercontinental ballistic missile that can reach the US mainland, and the combustible remnants of extremism in the Middle East and South Asia.

“I think violent extremism in some form is going to be with us for a long time,” he said. “Some people call it a generational problem. We called it a generational problem a generation ago, and it’s still with us.”

Dunford, who retired last Sept. 30, no longer is directly concerned with the country’s 1.3 million active-duty service members as part of his day-to-day portfolio. But after more than four decades in the military, he shares a bond with them that is unbreakable.

On this day, a former Marine-turned-contractor stopped by the house to check on the air-conditioning system. And there they were, the veteran and the retired Joint Chiefs chair, swapping memories of the Marine Corps.

Later, Dunford was asked if he can stop thinking about the challenges facing the United States, whether it’s possible as a civilian to set aside the full extent of the security concerns known to the Joint Chiefs chairman and few others.

“That’s an easy question to answer: No I can’t, because I care,” Dunford said, looking straight ahead, unflinching.

“I care about the world I’m going to live in. Your role changes, but you never stop caring. I care about the future of our country. Long after I’m gone.”