Leone began writing screenplays during the 1950s, primarily for the "sword and sandal" (or peplum) historical epics, popular at the time.

[13] When director Mario Bonnard fell ill during the production of the 1959 Italian epic The Last Days of Pompeii (Gli Ultimi Giorni di Pompei), starring Steve Reeves, Leone was asked to step in and complete the film.

[14] As a result, when the time came to make his solo directorial debut with The Colossus of Rhodes (Il Colosso di Rodi, 1961), Leone was well-equipped to produce low-budget films that looked like larger-budget Hollywood movies.

His film A Fistful of Dollars (Per un pugno di dollari, 1964) was based upon Akira Kurosawa's Edo-era samurai adventure Yojimbo (1961).

The look of A Fistful of Dollars was established by its Spanish locations, which presented a violent and morally complex vision of the American Old West.

In addition, Clint Eastwood stayed with the film series, joined later by Eli Wallach, Lee van Cleef, and Klaus Kinski.

Audience tension is maintained throughout this nearly three-hour film by concealing both the hero's identity and his unpredictable motivation until the final predictable shootout scene.

Perhaps unsurpassed as a retribution drama, the film's script was written by Leone and his longtime friend and collaborator Sergio Donati, from a story by Bernardo Bertolucci and Dario Argento, both of whom went on to have significant careers as directors.

Nevertheless, it was a huge hit in Europe, grossing nearly three times its $5 million budget among French audiences, and highly praised among North American film students.

[25][26] He devoted 10 years to this project, based on the novel The Hoods by former mobster Harry Grey, which focused on a quartet of New York City Jewish gangsters of the 1920s and 1930s who had been friends since childhood.

It was a meditation on another aspect of popular American mythology, the role of greed and violence and their uneasy coexistence with the meaning of ethnicity and friendship.

Joined by a freed slave and an Italian immigrant, Francesco, who arrives via the Port of Boston, they try desperately to avoid the battles of the ongoing war between the states.

The film was to have been a homage to classic writers from literature such as Edgar Lee Masters (Spoon River Anthology), Ambrose Bierce (An Occurrence at Owl Creek Bridge), Mark Twain (The Private History of a Campaign that Failed), Stephen Crane (The Red Badge of Courage), and Margaret Mitchell (Gone with the Wind), whose novel he had wanted to film a remake of.

Although the written treatment never got turned into a full screenplay, Leone's son Andrea had it published in a June 2004 issue of the Italian cinema magazine Ciak.

According to the documentary Once Upon a Time, Sergio Leone, the film opened in medias res as the camera goes from focusing on a Soviet hiding from the Nazis' artillery fire to panning hundreds of feet away to show the German Army Panzer divisions approaching the walls of the city.

The plot was to focus on an American photographer on assignment (whom Leone wanted to be played by Robert De Niro) becoming trapped in Leningrad as the German Luftwaffe begin to bombard the city.

Throughout the course of the film, he becomes romantically involved with a Soviet woman, whom he later impregnates, as they attempt to survive the prolonged siege and the secret police, because relationships with foreigners are forbidden.

[32] By 1989, Leone set the film's budget at $100 million, and had secured half of that amount in financing from independent backers from the Soviet Union.

Alex Cox offered to replace Leone as director, but was unable to secure the remaining $50 million required to produce the film.

[33] According to Frayling's biography of Leone, Something to Do with Death, he envisioned a contemporary adaptation of Cervantes' 17th-century novel Don Quixote with Clint Eastwood in the title role and Eli Wallach as Sancho Panza.

His relatives and close friends stated that he talked about filming a remake that was closer to the original novel, but it never advanced beyond discussions to any serious form of production.

[38] Leone was a fan of Louis-Ferdinand Céline's novel Journey to the End of the Night and was considering a film adaptation in the late 1960s; he incorporated elements of the story into The Good, the Bad and the Ugly and Duck, You Sucker!