The punk rock explosion of the mid-1970s seized the power of rock-and-roll back from the corporate conglomerates that had warped the music into a flabby, over-produced, stadium-rocking mess.

But it was Joe Strummer who made punk rock more than just an anarchic flail against the dying of the light. With The Clash, Strummer gave punk a militant, internationalist, pro-Black edge that made it matter not just as a musical statement but as a political one.

“It was The Clash that struck the strong political stance that really inspired a lot of people, and within The Clash he was the political engine of the band,” explained British singer Billy Bragg.

Strummer, who died Sunday from an apparent heart attack at age 50, was in on the ground floor of the punk moment. He saw a 1976 gig by the Sex Pistols and decided to start a band with Mick Jones and, after several personnel shifts, Paul Simonon and Topper Headon. By the summer of that year, The Clash was opening for the Pistols, and by the start of 1977 The Clash had a British hit with “White Riot.” Even on that first single, Strummer displayed the sensibilities that would come to define The Clash’s music: a reverence for radicalism, a faith in the power of direct action, an unyielding honesty and bluntness, a call to arms and a respect for rhythm that distinguished his band from most its contemporaries.

Written by Strummer and Jones at a time when British cities were experiencing a wave of urban riots, “White Riot” celebrated the revolt of Caribbean and African immigrants against the genteel racism of the British upper classes and asked why working-class whites didn’t join the fight. (“Black people gotta lot a problems/But they don’t mind throwing a brick/White people go to school/Where they teach you how to be thick…) The song’s class consciousness (“All the power’s in the hands/Of people rich enough to buy it…”) was matched by a demand for activism that pushed punk in a new and some thought dangerous direction (“Are you taking over/or are you taking orders?/Are you going backwards/Or are you going forwards?”).

The self-titled album that followed was so edgy that Columbia Records – the parent company of the band’s British label – refused to release it in the United States.

Barely two years later, however, with the release of “London Calling,” The Clash were suddenly being referred to by critics on both sides of the Atlantic as “The Only Band That Matters.” For a few years there, it was hard to argue with the description. The Clash helped to define the punk and new wave movements as explicitly anti-racist — working with ska and reggae bands to build the late-1970s Rock Against Racism movement in Britain.

Ultimately, however, the greatest political and cultural contributions made by Strummer and The Clash came in the form of the music. Fueled by Strummer’s fascination with the world’s music – born John Graham Mellor in Turkey, Strummer was the son of a British diplomat and spent much of his early life in Egypt, Mexico, Malawi and Iran – the band sampled widely from a diverse blend of musical styles.

Clash albums were infused with reggae, ska, funk and African rhythms, as well as with radical ideas about race, class and politics. Socialist, internationalist and angry, Strummer and The Clash started out by savaging British policies (especially those of a rising Tory politician named Margaret Thatcher) but they quickly found a bigger target in US foreign policy. The band’s epic, three-album 1980 release, “Sandinista!” — which was inspired by the Nicaraguan revolution of 1979 — was a fierce indictment of US policy in Latin American. One song, “Washington Bullets,” recalled the US role in the overthrow of the elected government of Chilean President Salvador Allende: “As every cell in Chile will tell/The cries of the tortured men,” Strummer growled. “Remember Allende, and the days before,/Before the army came/Please remember Victor Jara,/In the Santiago Stadium,/Es verdad – those Washington Bullets again.”

Strummer took pains to emphasize that he was a musician first – more a fan of Mott the Hoople than Marx, he liked to say. Yet, Strummer argued, it was impossible to avoid the reality of economic, racial and social injustice: “The politics were on the street in front of us, man,” he said, explaining that The Clash was forged in a moment when London was the home to refugees from Chile, as well as South Africans, Namibians and Zimbabweans who had fled white racist regimes in Africa

More than any other punk star, Strummer argued that the movement itself needed to be remembered as a radical break not just from increasingly pompous musical norms of the early 1970s but from a conservative mindset. “I will always believe in punk rock, because it’s about creating something for yourself,” he said in a July, 2002, interview. “Part of it was: ‘Stop being a sap! Lift your head up and see what is really going on in the political, social and religious situations, and try to see through the smoke screens.”

The Clash fell apart in the mid-1980s, after Strummer and Jones fell out. But the band’s influence grew – to a point where, next March, it will be inducted into the Rock and Roll Hall of Fame. For his part, Strummer retreated to rural England and slowly forged a solo career that ended up maintaining the values – both musical and political – of his best work with The Clash. His version of “Minstrel Boy” was a highlight of the “Black Hawk Down” movie soundtrack and the 2001 CD from Joe Strummer and the Mescaleros, “Global Ago-Go” was a brilliant multicultural mix flavored with Strummer’s best singing since his heyday with The Clash.

Strummer was working on a new Mescaleros release at the time of his death, along with a much-anticipated collaboration with U2’s Bono and Dave Stewart of The Eurythmics titled “48864.” That’s the number Nelson Mandela bore while imprisoned on South Africa’s Robben Island. The song was supposed to debut February 2, as part of a Robben Island benefit to help Mandela raise funds to fight AIDS in Africa.

Those who knew the man and his music were not at all surprised that Strummer’s last project was every bit as militant and globally-focused as his remarkable career.

“The thing about Strummer was he walked it like he talked it,” said Billy Bragg. “He didn’t cop out.”