This was new. Americans had never watched a president say goodbye to another president who was also his father. And the moment proved to be as personal as it was historic.

As George W. Bush spoke before the casket containing the body of George H.W. Bush at Washington National Cathedral on Wednesday, his face was a map of pain. He held his composure until the end of his eulogy. Then his voice shook and, finally, he broke down and sobbed.

Amid the commanders in chief, past and present, the honor guards and the trappings of state, the 43rd president at the pulpit was nothing more than a boy crying for his dad.

“Through our tears, let us know the blessings of knowing and loving you, a great and noble man, the best father a son or daughter could have,” Bush said, slumping in his grief.

There has long been speculation about the relationship between the first father and son to reach the White House since John Adams and John Quincy Adams two centuries ago. (The younger Adams learned of the elder’s death only after his burial.) Historians have scoured the path both Bushes took — Yale, stints flying fighter planes, the oil business and politics — for every sign of rivalry, jealousy and intrafamily psychodrama. Oedipus Tex.

But the reality was simpler, historians say, and was visible in George W. Bush’s grief, as the 43rd president remembered the 41st.

Dignitaries, politicians and family gathered at Washington National Cathedral on Dec. 5, to bid farewell to former president George H.W. Bush. (Jenny Starrs/The Washington Post)

“We tested his patience," his oldest son told mourners. “I know I did.”

Rather than Greek drama, the Bushes had an ordinary father-son bond that played out in extraordinary settings, these scholars contend. There were good times and bad, periods of distance and rebellion, the pain of loss and the joy of triumph. But whatever the weather, the climate was always loving.

“I think it was a tense relationship when George W. was in his sowing-his-wild-oats phase; and that was a pretty long phase,” said Jeffrey Engel, director of the Center for Presidential History at Southern Methodist University, who has interviewed both Bushes. “But by the end, they were peers.”

Presidential scholar Mark Updegrove spent years talking with the Bushes and those who knew them for his 2017 book about their relationship, “The Last Republicans.” Of all the anecdotes he collected, he finds one of the most telling to be a moment of everyday parenting: George and Barbara Bush were walking with their toddler son when little George went into a tantrum, wind-milling blows against his dad.

“His father just holds him at bay with a palm against his red forehead and until he tires out,” Updegrove said. “And then they just walk. There was a way in which George W. would transgress and his father would have the patience to know that his better angels would eventually take hold.”

Both presidents resisted any effort to “put them on the couch,” but the senior Bush left a rich emotional record in thousands of letters he wrote to family and friends through his life. In them, he makes clear the full play of fatherly emotion toward his often-rambunctious eldest child.

“Georgie has grown to be a near-man, talks dirty once in a while and occasionally swears, aged 4 1/2,” he wrote to his friend Gerry Bemiss soon after taking his family from Connecticut to Midland, Tex. “He lives in his cowboy clothes.”

And then when his son was 9: “Georgie aggravates the hell out of me at times (I am sure I do the same to him), but then at times I am so proud of him I could die,” he wrote to his father-in-law. “He is out for Little League — so eager. He tries so very hard. It makes me think back to all the times I tried out.”

In 1953, the boy was old enough to understand that tragedy had come to the family. His younger sister, Robin, had been sick. The Bushes had taken her to New York for treatment and one day months later, he was thrilled when they returned.

“I remember seeing them pull up and thinking I saw my little sister in the back of the car. I remember that as sure as I’m sitting here,” he told The Washington Post in a 1999 interview. “I run over to the car, and there’s no Robin.”

She had died of leukemia, a crushing loss that by all accounts brought the Bushes closer together as a couple and a family.

Soon after, George H.W. Bush began his political rise that took him from local party boss to Congress, national Republican chairman, U.N. ambassador and head of the CIA. His son, meanwhile, fell in line on the father’s path to the Ivy League and then back to Texas to look for oil.

It was a well-documented stretch of both work and partying for the younger Bush. His drinking produced some public embarrassments — including one 1985 episode in which he shouted profanity at Wall Street Journal reporter Al Hunt in a Dallas restaurant over a political story that he thought slighted his father, who was then in his second term as vice president.

The boozing was worrying his wife, Laura, and, Bush would say later, alcohol “was beginning to crowd out my energies.” But the elder Bush’s lofty roles also loomed large. “He looked in the mirror and said, ‘Someday I might embarrass my father,’ ” his friend Joe O’Neil recounted in Updegrove’s book.

George W. would quit cold turkey in July 1986. That same month, his father asked him to be a senior adviser to his presidential campaign.

“There is not one scintilla of evidence that he ever thought his son was badly wayward,” Updegrove said. “The narrative that George W. Bush was the family ne’er-do-well is vastly overblown.

”The younger Bush quickly became a full participant in the Bush apparatus, serving as pugnacious gatekeeper during the campaign and an enforcer of sorts in the White House.

“If he needed someone fired, it was often W. who did it,” Engel said.

Father and son had become political partners, even if there was a vast gulf between president and adviser. Remarkably, even that gap would close. Employing all the family assets — from fundraising to friendships — George W. began his own rapid political rise, from the governorship of Texas to, finally, the same Oval Office his dad had occupied.

If there was any rivalry in having to share the country’s highest title with his son, it didn’t show in the giddy, exuberant, detailed letter about George W.’s inauguration that the elder Bush wrote to his friend Hugh Sidey, a Time magazine writer. Friends were suddenly calling him “41.”

“It’s funny after all these years to get a new name; but, hey, what does it matter if your boy is the president of the United States of America so help me God,” he wrote.

They frequently called each other “Mr. President” when together, Engel said, a respectful joke open to no father and son but them.

History may have gotten its best insight into this remarkable relationship at the very end of it. In George H.W. Bush’s final minutes, they put a phone to his. It was George W. The dying man had not spoken in hours, but the younger hoped he would hear.

“ ‘Dad,’ I said, ‘I love you. You’ve been a wonderful father,' " George W. recounted during his eulogy.

And the last words the 41st president ever spoke were to the 43rd, a four-word epitaph of everything they meant to each other:

“I love you, too.”

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