When the Clash's song "London Calling" was recorded in late 1979, punk rock had already peaked. To jolt the genre, the Clash combined punk with reggae, rockabilly and soul, resulting in one of the era's most stirring and influential political rock anthems.

With its martial beat, rock-steady-funk bass line and lashing lyrics, the song warned about a world changing for the worse. Co-written by Mick Jones and the late Joe Strummer, the song "London Calling" never was a Billboard hit in the U.S.—though the...