The New Wave of British Heavy Metal (frequently abbreviated as NWOBHM or N.W.O.B.H.M.) is a period of heavy metal music that started in the late 1970s, in the United Kingdom, and achieved some international attention by the early 1980s. The era developed as a reaction in part to the decline of early heavy metal bands such as Deep Purple, Led Zeppelin and Black Sabbath. NWOBHM bands toned down the blues influences of earlier acts, increased the tempo, and adopted a tougher sound, taking a more hardcore approach to its music. Not intended to win a wide audience — it was a scene directed almost exclusively at heavy metal fans. The era is considered to be a main foundation for subsequent heavy metal sub-genres with acts such as Metallica citing NWOBHM bands like Diamond Head and Motörhead as a major influence on their musical style.