He lifted the plot from Akira Kurosawa’s Yojimbo (1961), which was itself lifted from Dashiell Hammett’s hardboiled crime novel, Red Harvest (1929).
Then, in 1964, Leone used his powerful visual style and a deathly desert setting to bring the screenplay to life and make the film that would forever define the genre. Over the next year or so Jamie Comas, Victor Catena, Tonino Valerii, Duccio Tessari, and Fernando Di Leo all contributed to it. Long lunch breaks got him fired from his second unit job on The Last Days of Sodom and Gomorrah (1962), and temporary unemployment got him the spare time needed to start writing the screenplay that would become Fistful of Dollars. If it wasn’t for Sergio Leone’s love of lengthy luncheons, the Spaghetti Western as we know it would not exist.