WASHINGTON >> Enraged and rattled by the political brawl over military mourning, White House Chief of Staff John Kelly returned this week to the one place he could go clear his head: Section 60 of Arlington National Cemetery, some of the saddest ground in America. There, amid the memorials to the recent war dead, is Grave 9480, the final resting place of Kelly’s son, Robert, a Marine killed in 2010 in Afghanistan.

“The only thing I could do to collect my thoughts was to go and walk among the finest men and women on this earth,” Kelly told reporters today as he mounted a vigorous defense of President Donald Trump’s handling of the “sacred” job of consoling families of fallen soldiers.

Kelly’s remarks invoking his son and his personal grief was a startling shift for the reserved, retired Marine general who has largely recoiled at injecting his family’s loss into the political arena. Since the younger Kelly was killed by a land mine in remote Helmand province, his father has labored to keep Robert’s death out of the spotlight — no easy task as the highest-ranking military official to lose a child in the wars. Kelly only occasionally references his son in remarks, often growing emotional as he recounts the heartbreaking events or is asked to describe Robert.

“Finest man I ever knew,” Kelly said on “Fox & Friends” in May.

On Memorial Day he and Trump visited Robert’s grave at Arlington.

“We grieve with you, we honor you and we pledge to you that we will always remember Robert and what he did for all of us,” Trump said, singling out the Kelly family during his remarks to the nation that day. Turning to Robert’s father, then the secretary of homeland security, Trump added, “Thank you, John.”

But Trump this week pushed Kelly into new terrain.

Seeking to defend his record of outreach to Gold Star families, Trump suggested former President Barack Obama should have called Kelly after Robert’s death but didn’t.

“You could ask Gen. Kelly, did he get a call from Obama?” Trump said in an interview on Fox News Radio.

Trump’s willingness to raise the tragedy set many in the military community seething.

“If there is one sacred ground in politics it should be the ultimate sacrifices made by our military,” wrote Chuck Hagel, a defense secretary under Obama and, before that, a Republican U.S. senator. In an email to The Associated Press, Hagel added, “To use General Kelly and his family in this disgusting political way is sickening and beneath every shred of decency of presidential leadership.”

“I would be surprised if he comes in and starts allowing people to use his family as a tool,” said Charles C. Krulak, a former Marine Corps commandant who has known John Kelly since the mid-1990s.

The public controversy this week clearly was painful for Kelly, whose son had been awarded the Purple Heart. Kelly knew in 2010 that his son was patrolling with his men through mine-filled battlefields and had just days earlier warned the family of the potential danger, according to a report in The Washington Post. When Gen. Joseph Dunford Jr. rang the elder Kelly’s doorbell at 6:10 a.m. Nov. 9, 2010, John Kelly knew Robert was dead. Dunford, Kelly told reporters Thursday, said Robert “was where he wanted to be exactly, what he wanted to be with exactly the people he wanted to be with.”

“Hours after my son was killed, his friends were calling us from Afghanistan telling us how great a guy he was. Those are the only phone calls that really matter,” Kelly said Thursday. But, he allowed, there’s “not really much that can take the edge off” such a loss.

In March 2011 Kelly accompanied his boss, Defense Secretary Bob Gates, on a visit to the Sangin district, in Helmand province — the scene of some of the most intense fighting of the war and where Robert Kelly had been killed.

As Gates’ senior military assistant, Kelly stood silently among young Marines gathering under a harsh sun as Gates applauded what they had accomplished.

“Your success, obviously, has come at an extraordinary price,” Gates said without mentioning names.

Asked to elaborate on Robert in the Fox interview, Kelly hesitated at first — then it came tumbling out.

“Finest guy. Wonderful guy. Wonderful husband, wonderful son, wonderful brother. Brave beyond all get-out. His men still correspond with us. They still mourn him as we do.”