Pianist Van Cliburn, one of the most celebrated musicians of the 20{+t}{+h} century and a resident of Fort Worth since 1986, died Wednesday morning at his mansion near Fort Worth at age 78. He had been diagnosed with advanced and aggressive bone cancer.

In an unprecedented intersection of music, media and Cold War politics, Mr. Cliburn burst on the international scene in 1958 as winner of the first Tchaikovsky International Competition in Moscow. The competition was widely assumed to be a showcase for pianists from Russia and its satellite countries. The surprising triumph of a tall, gangly, wavy-haired Texan, all soft-spoken politeness, was splashed all over newspapers, magazines and then-new television screens. A Time magazine cover hailed “The Texan Who Conquered Russia.”

So daring was the jury’s choice that it required the approval of the Soviet Union’s new premier, Nikita Khrushchev. But the 23-year-old pianist, whose playing had an unhurried grandeur that seemed from another age, had already enchanted the Moscow audiences. In years to come, his repeated returns to Russia would continue to draw adoring crowds. Mr. Cliburn became, in effect, a powerful ambassador for peace between two rival superpowers.

“Van looked and played like some kind of angel,” the Russian pianist Andrei Gavrilov told Cliburn biographer Howard Reich. “He didn’t fit the evil image of capitalists that had been painted for us by the Soviet government.”

Back home, he was feted with a ticker-tape parade on Wall Street. Taxi drivers and waitresses who couldn’t have identified Tchaikovsky’s 1812 Overture keenly followed the new star’s career. Generations of pianists would be inspired by Mr. Cliburn’s glamorous example.

“He brought music to millions of people who heretofore had not been exposed to classical music,” said Richard Rodzinski, former executive director of the Van Cliburn Foundation, which runs the competition named for the pianist. “The extraordinary popularity that he enjoyed, having recorded the first record to go platinum, having then become virtually a household name -- I don’t believe any other performer in America achieved that status. I don’t think even Leonard Bernstein had that kind of popularity.”

With orchestras, concert presenters and audiences clamoring for his appearances, at top fees, and with the postwar proliferation of air travel, Mr. Cliburn booked a dizzying schedule of concerts and recordings. The frantic pace took its toll, though, and by the early 1970s some critics were noticing a loss of freshness.

“There were a great number of concerts that people wanted,” the pianist recalled in a 2008 interview. “I said, ‘If I have the strength, I’ll try to do this.’ … It isn’t difficult to play the concert if you can get there and be rested. That wasn’t always the case.”

After the deaths of two of the men closest to him, his father Harvey and the impresario Sol Hurok, Mr. Cliburn began turning down engagements, and 20 years after the Moscow triumph he withdrew from concertizing.

As he told a Vogue interviewer, he got “tired of living out of a suitcase, flying nearly every day, never having a home. I could never go to the opera, which I adore, or a friend’s concert, or a movie. By 1978 I was ready to be bored for a while, to have a regular life. I wanted a house with all my things around me.”

Wise investments of the considerable income from his concert career facilitated a luxurious sabbatical. Having filled multiple rooms of New York’s Salisbury Hotel, in 1986 he and his mother moved to the 18-acre Westover Hills estate that had belonged to Kay Kimbell, the Fort Worth entrepreneur who had endowed the Kimbell Art Museum.

He already had many friends in Fort Worth, where in 1962 the quadrennial Van Cliburn International Piano Competition was inaugurated in his honor. He served as an artistic adviser to the competition, to be held again in May and June 2013, and he took a keen interest in its winners’ careers.

With the aura of an old-school Southern gentleman, with a velvety baritone voice, Mr. Cliburn became Fort Worth royalty. He was as warmly gracious to the youngest piano student as to the city’s movers and shakers.

“He was a true, true gentleman,” Rodzinski said, “genuinely modest, self effacing, always surprised at people remembering him, appreciating him. Generosity, modesty, gentleness, incredibly loyalty as a friend, great, great kindness — these were the attributes that made people so terribly fond him.”

In 1989, Mr. Cliburn started to revive his concert career, and he performed that September at the opening of Dallas’ Meyerson Symphony Center. He again appeared with major orchestras and continued to draw rapturous audiences, but the old magic appeared only intermittently. The rich tone of his earlier years had hardened, his memory and technique had become less reliable and his interpretations had become fussy, mannered. A couple of onstage fainting spells made headlines.

“Something died there,” Bryce Morrison, a British critic specializing in piano performance, said in a 2004 interview. “I do think he was a victim of his own success, a victim of a commercial thing that can make you and destroy you at the same time. It wasn’t a very long career before things started to crack.”

Still, honors continued to pour in: the Kennedy Center Honors, a Presidential Medal of Freedom, a lifetime achievement award at the Grammy Awards.

Born July 12, 1934 in Shreveport, La., Harvey Lavan Cliburn Jr. was the son of an oilman and a piano teacher who had studied with Arthur Friedheim, a Russian-born protégé of Franz Liszt. When he was 6, the family moved to the oil boomtown Kilgore, in East Texas.

Mr. Cliburn’s mother, Rildia Bee O’Bryan Cliburn, would be his most enduring influence. Even after the young pianist went off to New York’s Juilliard School to study with the formidable Russian teacher Rosina Lhévinne, Mrs. Cliburn would remain his musical coach and career adviser until her death in 1994. They both loved staying up much of the night and sleeping much of the day, and with her Texas wit Mrs. Cliburn could be the life of any party.

Mr. Cliburn carefully guarded Southern gentleman aura cracked a bit in 1996, when he was hit with a multimillion-dollar palimony suit by a man claiming a 17-year personal and professional relationship with the pianist. Mr. Cliburn dismissed the suit’s “salacious accusations,” and it was thrown out for lack of a written contract. In more recent years, Mr. Cliburn’s companion has been Thomas L. Smith.

In his heyday, Mr. Cliburn was nothing if not a distinctive artist. In an age of “anything you can play, I can play faster,” his performances were majestic. While crackerjack American pianists all around him favored bright, brittle tones and crisp, abstract performances, Mr. Cliburn caressed glowing sonorities out of the piano and seemed to suggest the interpretive warmth of ages gone by.

“He was able to put across his generosity of spirit in his performances,” Rodzinski said. “His desire was to play for people. When he said that half of you always has to be in the audience, he really meant that. That’s why he had such extraordinary appeal and success in Russia. The audiences felt that generosity of spirit, that real love and communicative quality, and that made them love him.”

If many of his later recordings seem more respectful than inspired, his 1958 recording of one of his signature pieces, the Tchaikovsky First Concerto, with the conductor Kirill Kondrashin, evokes grandeurs of imperial Russia. Another recording with Kondrashin, of the Rachmaninoff Third Concerto, captures sheer magic in a daringly slow middle movement. Among solo recordings, the 1960 Rachmaninoff Second Sonata fairly explodes with passion.

If Mr. Cliburn didn’t quite achieve the elusive second act, the glow of the first never really died out. Among classical musicians of the last 60 years, only he and the late Luciano Pavarotti whipped up the kind of widespread excitement usually reserved for rock stars. If critics, especially in later years, sometimes pursed their lips, audiences still leapt to their feet, ecstatic at having witnessed a legend.

“Music is such a part of life,” the ever-effusive Mr. Cliburn said in a 2008 interview. “It’s like breathing, like nourishment. And the classics are so important, because within the realm of classical music you have eternity and infinity, and mathematics and architecture, and spirituality and wonderment — so many things.”

Van Cliburn: A life in music

1934: Born Harvey Lavan Cliburn Jr., July 12, in Shreveport, La.

1941: Moves with family to Kilgore, Texas

1951: Graduates from Kilgore High School, enrolls in Juilliard School in New York.

1954: Wins Levintritt Award, which includes a New York Philharmonic debut; graduates from Juilliard.

1958: Wins the first International Tchaikovsky Competition in Moscow, getting worldwide news coverage and a ticker-tape parade in New York.

1962: Organized by Fort Worth fans, the Van Cliburn International Piano Competition debuts in Fort Worth. Mr. Cliburn remains an adviser to the competition the rest of his life.

1978: Begins hiatus from concertizing and recording.

1986: Moves from New York to Fort Worth

1987: Plays at the White House for President Reagan and Soviet president Mikhail Gorbachev.

1989: Resumes performing with concerts with the Philadelphia Orchestra, Moscow Philharmonic and, at the dedication of the Meyerson Symphony Center, the Dallas Symphony Orchestra.

2001: Kennedy Center Honors

2003: Presidential Medal of Freedom

2004: Russian Order of Friendship, the nation’s highest civilian honor

2011: National Medal of the Arts and Grammys’ Lifetime Achievement Award

2012: Diagnosed with advanced bone cancer.