Although the subgenre has its roots in the films of the late 1960s, it was influenced by such rough-edged American police thrillers of the early 1970s. With directors such as Fernando Di Leo and Umberto Lenzi and actors such as Maurizio Merli and Tomas Milian, poliziotteschi films became popular in the mid-1970s after the decline of spaghetti Westerns.