Robert Vaughn, who starred as Napoleon Solo on TV’s “The Man From U.N.C.L.E.” from 1964-68, died Friday morning of acute leukemia, his manager Matthew Sullivan told Variety. He was 83.

Vaughn began undergoing treatment for the illness this year on the East Coast.

The James Bond-influenced “The Man From U.N.C.L.E.,” in which Vaughn’s Solo and David McCallum’s Illya Kuryakin battled the evil forces of T.H.R.U.S.H. around the globe (thanks to the glories of stock footage), was quite the pop-culture phenomenon in the mid-1960s, even as the show’s tone wavered from fairly serious to cartoonish and back again over its four seasons.

It spawned a spinoff, “The Girl From U.N.C.L.E.,” starring Stefanie Powers, as well as a few feature adaptations during the run of the TV series — “One Spy Too Many,” “One of Our Spies Is Missing,” and “The Karate Killers” — that starred Vaughn and McCallum. Vaughn also guested as Napoleon Solo on sitcom “Please Don’t Eat the Daisies” and made an uncredited appearance as Solo in the 1966 Doris Day feature “The Glass Bottomed Boat”; he reprised the role in 1983 TV movie “The Return of the Man from U.N.C.L.E.: The Fifteen Years Later Affair.”

A Guy Ritchie-directed feature adaptation of “The Man From U.N.C.L.E.” was released in August 2015 with Henry Cavill and Armie Hammer starring as Solo and Kuryakin, respectively.

Vaughn vaulted into the public eye with his vaunted performance in the soapy 1959 Paul Newman feature “The Young Philadelphians,” for which Vaughn was deservedly Oscar nominated for best supporting actor.

In the film, Newman’s character is pursuing his Machiavellian way to the top of Philadelphia’s upper crust when he sees his friend, played by Vaughn, manipulated by said upper crust into alcoholism and an unjust murder charge. The New York Times said, “Robert Vaughn, as Newman’s sick and ill-used friend, adds a striking bit in incoherently explaining his dire predicament.”

The next year he was one of the stars of John Sturges’ “The Magnificent Seven,” a remake of Akira Kurosawa’s “Seven Samurai,” along with Yul Brynner, Steve McQueen, and Charles Bronson. The success of the Western certainly boosted the actor’s profile, but his brand of sophisticated urbanite did not mesh well with a career in Westerns. (Though when the enduringly popular film was adapted into a TV series in 1998, Vaughn returned in the recurring role of Judge Oren Travis, and when the material was contemporized and turned into the story of a British soccer team in a 2013 film called “The Magnificent Eleven,” the actor duly starred as the villain, a gangster named American Bob.) Antoine Fuqua also directed a remake of the film, starring Denzel Washington and Chris Pratt, this year.

In 1968, after appearing in the movie spinoffs from “The Man From UNCLE,” Vaughn appeared in McQueen vehicle “Bullitt” as the politician who’s out for the head of McQueen’s cop while pressure mounts from other directions as well (and a lot of nifty car chases around San Francisco are offered up).

He did several films in a row at this point: comedy “If It’s Tuesday, This Must Be Belgium” (1969); WWII drama “The Bridge at Remagen,” in which he played the Nazi commander (the New York Times said: “Mr. Vaughn, as the tense commander across the water, is excellent”); a feature adaptation of “Julius Caesar” that starred John Gielgud, Charlton Heston, and Jason Robards, and in which Vaughn played Servilius Casca; the interesting sci-fi drama “The Mind of Mr. Soames,” in which Terence Stamp played a man, in a coma since birth, who’s brought to consciousness by an American doctor played by Vaughn, who soon spars with the British team supervising him over his care; and 1971’s “The Statue” and “Clay Pigeon.”

From 1972-74 he did his third stint as the star of a TV series with “The Protectors,” playing Harry Rule, one of three freelance troubleshooters who run an international crime-fighting agency based in London.

In 1974, as the show ended, he did two feature films: “The Man From Independence,” in which Vaughn played Harry S. Truman, and disaster movie “The Towering Inferno,” in which he played Senator Parker, who helps out once the blaze starts.

During the 1970s Vaughn capitalized on the era of the miniseries, appearing in NBC’s highly regarded 1976 entry “Captains and the Kings”; ABC’s “Washington: Behind Closed Doors” (1977), for which he received his first Emmy nomination; NBC’s “Backstairs at the White House,” in which the actor played President Woodrow Wilson, for which he was also Emmy nominated; NBC’s “Centennial,” in which he played the wealthy, opportunistic Morgan Wendell; ABC’s “Inside the Third Reich” (1982); and CBS’ “The Blue and the Gray” (1982).

Having played Woodrow Wilson, he now played Franklin Delano Roosevelt in the 1982 HBO adaptation of the Dore Schary one-man play “FDR: That Man in the White House” (a role he reprised in the 1986 telepic “Murrow,” starring Daniel J. Travanti as Edward R. Murrow) and Gen. Douglas MacArthur in the Australian-made, PBS-aired miniseries “The Last Bastion” in 1984.

The actor was now regularly playing senators and other powerful men who were often given to scheming and nefarious motives: Vaughn played one such fellow as the villain in 1983’s “Superman III.”

He recurred on the series “Emerald Point N.A.S.,” starring Dennis Weaver, in 1983-84.

Vaughn was brought aboard the sagging NBC series “The A-Team” in its final season in 1986-87 as the network changed the flavor of the show. The actor played General Hunt Stockwell, a mysterious operative for the CIA for whom the team would now work, often abroad, in “Mission: Impossible”-like scenarios. (One episode was titled “The Say U.N.C.L.E. Affair.”)

He was still working in features; Vaughn starred as Adolf Hitler in the obscure 1989 comedy “That’s Adequate” and as Lord Byron Orlock in the comedy “Transylvania Twist” the same year. He kept busy, too, with guest appearances on “Murder, She Wrote,” “Walker, Texas Ranger,” and “The Nanny.”

While “Law & Order” afforded many an actor with an opportunity to demonstrate his or her own skills, Vaughn was particularly memorable in his three-episode 1997-98 arc as Carl Anderton, a man as powerful as he is certifiably crazy and stubborn. What begins as Anderton’s refusal to acknowledge that mental illness excused his grandson’s otherwise criminal behavior — and that a propensity for paranoia may have been passed down genetically from him — escalates into a campaign to remove D.A. Adam Schiff from office.

More recently he was memorable in two unrelated performances on “Law & Order: SVU”; in 2015 episode “December Solstice,” he played a celebrity author who becomes the object of a legal battle over his welfare between his new wife and his daughters from a previous marriage.

Vaughn brought his trademark brand of villainy to the David Zucker comedy “BASEketball” in 1998 and to Louis C.K.’s comedy “Pootie Tang” in 2001.

From 2004-12 Vaughn starred in the BBC-AMC co-production “Hustle,” a stylish if derivative dramedy series about a group of London con artists who pull off elaborate stings.

In 2012 he did a 13-episode arc on the U.K. soap “Coronation Street,” in which he played Milton Fanshaw, an American restaurant owner who proves a love interest for one of the main characters, tempting her to come back with him to the U.S.

Robert Francis Vaughn was born in New York City to parents in show business, his father a radio actor and his mother an actress on the stage.

He went to high school in Minneapolis and attended the University of Minnesota, where he majored in journalism, but quit after a year. Moving to Los Angeles, he studied drama at Los Angeles City College, then transferred to Cal State L.A. and completed his Master’s degree. Subsequently — and while having already started a busy acting career in the 1960s and into the 1970s — he completed a Ph.D. in communications at USC. The subject of his thesis was the blacklisting of Hollywood entertainers during the McCarthy era, and it was published in 1972 as “Only Victims.”

He made his small-screen debut way before the days of “U.N.C.L.E.,” guesting on NBC’s Richard Boone vehicle “Medic” in 1955 and was soon busy guesting on shows ranging from “Father Knows Best” to “Gunsmoke,” and “The Rifleman” to “Dragnet,” and “Mike Hammer.”

Meanwhile, he made his big-screen debut in an uncredited role in Cecil B. DeMille’s 1956 epic “The Ten Commandments” and there soon followed roles in Western “Hell’s Crossroads” and “No Time to Be Young,” a juvenile crime drama in which he starred. But his performance in “The Young Philadelphians” and the acclaim he received for it changed everything.

He is survived by wife Linda Staab, to whom he had been married since 1974, and two adopted children: son Cassidy and daughter Caitlin.