information:extraction
Adventure films and dramatic spectacles

In 1939, DeMille's Union Pacific was successful through DeMille's collaboration with the Union Pacific Railroad. The Union Pacific gave DeMille access to historical data, early period trains, and expert crews, adding to the authenticity of the film. During pre-production of Union Pacific, DeMille was dealing with his first serious health issue. In March 1938, he underwent a major emergency prostatectomy. He suffered from a post-surgery infection from which he nearly did not recover, citing streptomycin as his saving grace. The surgery caused him to suffer from sexual dysfunction for the rest of his life, according to some family members. Following his surgery and the success of Union Pacific, in 1940, DeMille first used three-strip Technicolor in North West Mounted Police. DeMille wanted to film in Canada; however, due to budget constraints, the film was instead shot in Oregon and Hollywood. Critics were impressed with the visuals but found the scripts dull, calling it DeMille's "poorest Western". Despite the criticism, it was Paramount's highest-grossing film of the year. Audiences liked its highly saturated color, so DeMille made no further black-and-white features. DeMille was anti-communist and abandoned a project in 1940 to film Ernest Hemingway's For Whom the Bell Tolls due to its communist themes, despite the fact he had already paid $100,000 for the rights to the novel. He was so eager to produce the film that he hadn't yet read the novel. He claimed he abandoned the project in order to complete a different project, but in reality, it was to preserve his reputation and avoid appearing reactionary. While concurrently filmmaking, he served in World War II at the age of sixty as his neighborhood air-raid warden.

In 1942, DeMille worked with Jeanie MacPherson and brother William deMille in order to produce a film called Queen of Queens, which was intended to be about Mary, mother of Jesus. After reading the screenplay, Daniel A. Lord warned DeMille that Catholics would find the film too irreverent, while non-Catholics would have considered the film Catholic propaganda. Consequently, the film was never made. Jeanie MacPherson would work as a scriptwriter for many of DeMille's films. In 1938, DeMille supervised the compilation of film Land of Liberty to represent the contribution of the American film industry to the 1939 New York World's Fair. DeMille used clips from his own films in Land of Liberty. Though the film was not high-grossing, it was well-received, and DeMille was asked to shorten its running time to allow for more showings per day. MGM distributed the film in 1941 and donated profits to World War II relief charities.

In 1942, DeMille released Paramount's most successful film, Reap the Wild Wind. It was produced with a large budget and contained many special effects including an electronically operated giant squid. After working on Reap the Wild Wind, in 1944, he was the master of ceremonies at the rally organized by David O. Selznick in the Los Angeles Coliseum in support of the Dewey – Bricker ticket as well as Governor Earl Warren of California. DeMille's subsequent film Unconquered (1947) had the longest running time (146 minutes), longest filming schedule (102 days), and largest budget ($5 million). The sets and effects were so realistic that 30 extras needed to be hospitalized due to a scene with fireballs and flaming arrows. It was commercially very successful.

DeMille's next film, Samson and Delilah in 1949, became Paramount's highest-grossing film up to that time. A Biblical epic with sex, it was a characteristically DeMille film. Again, 1952's The Greatest Show on Earth became Paramount's highest-grossing film to that point. Furthermore, DeMille's film won the Academy Award for Best Picture and the Academy Award for Best Story. The film began production in 1949, Ringling Brothers-Barnum and Bailey were paid $250,000 for use of the title and facilities. DeMille toured with the circus while helping write the script. Noisy and bright, it was not well-liked by critics, but was a favorite among audiences. DeMille signed a contract with Prentice Hall publishers in August 1953 to publish an autobiography. DeMille would reminisce into a voice recorder, the recording would be transcribed, and the information would be organized in the biography based on the topic. Art Arthur also interviewed people for the autobiography. DeMille did not like the first draft of the biography, saying that he thought the person portrayed in the biography was an "SOB"; he said it made him sound too egotistical. Besides filmmaking and finishing his autobiography, DeMille was involved in other projects. In the early 1950s, DeMille was recruited by Allen Dulles and Frank Wisner to serve on the board of the anti-communist National Committee for a Free Europe, the public face of the organization that oversaw the Radio Free Europe service. In 1954, Secretary of the Air Force Harold E. Talbott asked DeMille for help in designing the cadet uniforms at the newly established United States Air Force Academy. DeMille's designs, most notably his design of the distinctive cadet parade uniform, won praise from Air Force and Academy leadership, were ultimately adopted, and are still worn by cadets.