Iron Maiden released their second studio album, Killers, on 16 February 1981 in the United Kingdom by EMI Records. It was later released on 11 May in the United States by Harvest and Capitol Records.
 
The album marked the debut of guitarist Adrian Smith and the departure of vocalist Paul Di'Anno, who was let go due to issues with his live performances stemming from his substance abuse. Killers was also the first Iron Maiden album produced by Martin Birch, who continued to work with the band on their next eight albums.