The film predates Rambo (1982), the film which introduced audiences to the John Rambo of David Morrell by seven years. Tomas Milian happened to read David Morrell's novel while flying from the U.S. to Rome. Loving the story he tried to talk some Italian producers into making a film out of it, with him starring as John Rambo. Nothing came of this, but he was allowed to use the Rambo moniker in the next poliziottesco he starred in, Bracelets de sang (1975). The film does not borrow elements from the novel, with Umberto Lenzi stating he was more influenced by the crime films of Don Siegel.