Sen. John McCain, the former POW and outspoken Republican politician nicknamed The Maverick for being unafraid to disagree with fellow members of his party, has died. He was 81.

“Senator John Sidney McCain III died at 4:28 p.m. on August 25, 2018,” his family said in a statement Saturday, according to NBC News.

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In an emotional tweet, his wife Cindy, 64, wrote, “My heart is broken. I am so lucky to have lived the adventure of loving this incredible man for 38 years. He passed the way he lived, on his own terms, surrounded by the people he loved, in the place he loved best.”

His daughter Meghan McCain, 33, was among the people praising McCain on social media in the wake of his death. “In the thirty-three years we shared together, he raised me, taught me, corrected me, comforted me, encouraged me, and supported me in all things,” she wrote in part. “He taught me how to live. His love and his care, ever present, always unfailing, took me from a girl to a woman — and he showed me what it is to be a man.”

On Friday, his family announced that McCain, “with his usual strength of will,” decided to stop treatment for the stage-four brain cancer he had been battling since its diagnosis last summer.

“In the year since,” the McCain family said, “John has surpassed expectations for his survival. But the progress of disease and the inexorable advance of age render their verdict.”

In July 2017, McCain revealed that he had been diagnosed with glioblastoma, the most aggressive form of brain cancer, just days after he underwent surgery to remove a blood clot above his eye.

McCain later revealed during a September 2017 interview with 60 Minutes that he asked doctors to be forthright about his health.

“Some say 3 percent, some say 14 percent. You know it’s — it’s a very poor prognosis,” he said. “So I just said, ‘I understand. Now we’re going to do what we can, get the best doctors we can find and do the best we can, and at the same time celebrate with gratitude a life well lived.’ ”

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Months later, as McCain continued his battle against brain cancer, his daughter Meghan paid tribute to her father and his “Viking” fighting spirit in a touching Instagram post in May.

“My Mother calls me ‘John McCain in a dress’ – my relationship with my father has always been magic – we are fiercely and protectively forever on each other’s team,” Meghan captioned a smiling photo with her father. “Love with your complete and whole heart in this life. We keep fighting because we are all McCains, we are a family of a long lineage of Vikings – fighting is what we have always done, and what we will always do.”

Born in August 1936 at the U.S. air base in Panama, McCain was the son and grandson of two four-star U.S. Navy admirals. He ultimately followed in their footsteps, enrolling at the U.S. Naval Academy in Annapolis, Maryland, in 1954.

As a naval pilot, he was deployed on the USS Forrestal to the Gulf of Tonkin in Vietnam, where he was ultimately taken as a prisoner of war in October 1967. McCain was captured by the North Vietnamese after his plane was shot down by a missile. According to McCain, the plane entered an “inverted, almost straight-down spin,” and he ejected, breaking both his arms and his leg in the process.

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While held captive at Hanoi’s Hoa Lo prison, McCain was denied medical attention and repeatedly tortured by his captors. “They left me on the floor of a cell for four days, during which time I lapsed in and out of consciousness,” McCain told PEOPLE back in 1992. “Their policy was that they wouldn’t provide any medical treatment unless you gave them military information. I would only give them my name, rank, serial number and date of birth. And so, after about four days on the floor of the cell, they got nothing out of me because I kept passing out.”

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McCain refused to cooperate, and remained at the prison for more than five years – spending much of that time in solitary confinement.

He recalled to PEOPLE, “they treated me pretty badly,” revealing further that he was suffering from dysentery and was being beaten every two hours in order to get him to sign confessions and make audio recordings trashing America.

He was released in March of 1973, but still bore some of the injuries from his harrowing ordeal.

“Unlike some, I was fortunate that I was able to put it all behind me when I came home,” he said. “People ask me how long did it take to readjust? It took me about 45 minutes. I never had a nightmare or a flashback or anything like that. I know a lot of my friends were not so fortunate, who never fully came back from that experience. But I did.”

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After returning home, McCain regained his naval flight status and was named the naval liaison to the U.S. Senate in 1977 before ultimately retiring from duty in 1981. During his service, McCain was awarded the Purple Heart and the Distinguished Flying Cross, among other honors, according to his website.

McCain was first elected to the U.S. House of Representatives in Arizona in 1982, serving two terms before being elected as state senator in 1986.

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After more than a decade in the Senate, McCain ran for the Republican presidential nomination in 2000 but lost to primary opponent George W. Bush.

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McCain went on to become the 2008 Republican nominee for president alongside running mate Sarah Palin; he lost to Barack Obama. While McCain continued to defend Palin’s performance in a new book and documentary set to be released in May, he also said he regretted not picking former Senator Joseph I. Lieberman as his running mate in 2008, according to The New York Times. McCain said “my gut told me” to choose Lieberman instead of Palin and “I wish I had.”

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Leading up to his death, McCain served as the chairman of the Senate Committee on Armed Services, a member of the Senate Committee on Indian Affairs and a member of the Senate Committee on Homeland Security and Governmental Affairs.

In July, McCain underwent surgery to remove a blood clot above his eye.

The surgery went well but had massive reverberations in Washington, forcing GOP Senators to postpone a vote on the controversial Republican bill to replace Obamacare until McCain could return.

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The senator revealed his diagnosis in July, and one day after doing so he returned to Twitter and promised he’d be back on the Senate floor.

“I greatly appreciate the outpouring of support — unfortunately for my sparring partners in Congress, I’ll be back soon, so stand-by!” He said. Just five days later, he kept his promise and returned to thunders applause from people in both parties.

While he was welcomed back, he proved to still by The Maverick when he refused to support the Graham-Cassidy bill to repeal the Affordable Care Act in September, which drew sharp criticism from President Donald Trump as others hailed him a hero.

After the vote, McCain went back to receiving chemotherapy treatments in Phoenix, Arizona, to slow the progression of the disease. He completed his first round of radiation in August 2017.

In December, McCain was hospitalized for “normal side effects of his ongoing cancer therapy,” his office said. But to the excitement of his family, he was able to come home to Arizona for Christmas.

In February, Meghan said that her father had a “crazy amazing recovery.”

“He is in Sedona, Arizona, right now at our ranch doing physical therapy and he has amazing doctors and he’s doing really well,” she said on The Late Show with Stephen Colbert. “He had a sort of rough time at Christmas and he’s made this crazy amazing recovery which I guess I shouldn’t be surprised at, he is so resilient in so many different ways. He’s a tough bastard.”

He continued physical therapy at home in Arizona for the next few months, until he had to return to the Mayo Clinic in April for an emergency surgery.

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“On Sunday, Senator McCain was admitted to Mayo Clinic in Phoenix, Arizona, and underwent surgery to treat an intestinal infection related to diverticulitis,” his office said. Meghan added that he was in “stable” condition.

Later that month, McCain shared an excerpt from his new book, in which he admitted that his brain cancer diagnosis gave him an “ungentle persuasion” to realize that his current term in office would be his last, and pushed him to change the way he votes.

“I’m freer than colleagues who will face the voters again. I can speak my mind without fearing the consequences much. And I can vote my conscience without worry,” McCain said. “I don’t think I’m free to disregard my constituents’ wishes, far from it. I don’t feel excused from keeping pledges I made. Nor do I wish to harm my party’s prospects. But I do feel a pressing responsibility to give Americans my best judgment.”

Before his death, McCain enjoyed spending time on the deck at his Arizona ranch, visiting with a constant flow of friends, including former Vice President Joe Biden, The New York Times reported in May. Biden said the two reminisced about the “crazy senators” they had served with, the overseas trips they took together, and the friendship between McCain and Biden’s two sons. Biden’s son Beau died of glioblastoma, the same rare brain cancer McCain had, in May 2015.

Biden also said that, even as McCain battled brain cancer and the debilitating side effects of his treatment, the senator was still worried about the state of the nation under President Trump’s administration.

“Here John knows he’s in a very, very, very precarious situation, and yet he’s still concerned about the state of the country,” Biden said in an interview with the Times. “We talked about how our international reputation is being damaged and we talked about the need for people to stand up and speak out.”

According to the same Times report, people close to McCain allegedly told the White House “that their current plan” was to invite Vice President Mike Pence to the funeral service, but not Trump, citing the pair’s “rocky relationship.”

During the visits, friends told McCain they loved him and how much he’d meant to them but didn’t explicitly say goodbye. The senator “doesn’t like overt sentimentality,” his friend, the former chief of staff Grant Woods, said. Nevertheless, the visits often ended with McCain saying, “I love you,” the Times reported.

McCain also enjoyed quiet moments sitting out on his deck with his wife, listening to the hummingbirds and the burbling stream that runs through their 15-acre ranch.

“He finds real solace there,” Biden said.

McCain is survived by wife Cindy, and his children: Douglas, Andrew, and Sidney (all with first wife Carol McCain) and Meghan, Jack, James, and Bridget, with Cindy.

Just days before Thanksgiving, McCain gave away daughter Meghan, a co-host on The View, at her wedding to conservative pundit Ben Domenech at the family’s ranch in Sedona, Arizona.

Opening up to PEOPLE about the wedding and his legacy, McCain said in late November, “I have been so fortunate to have the life that I have had, full of time and adventure and excitement.