One of his first assignments in Hollywood was when he found work as an extra in All Quiet on the Western Front (1930), although he was fired from the production for talking back to the director, Lewis Milestone. After some success with short films, he graduated to features in 1942, turning out two crisp B mysteries, Eyes in the Night and Kid Glove Killer before getting his big break with The Seventh Cross (1944), a top-notch A picture starring Spencer Tracy, and his first hit.

He directed many different film genres including thrillers, westerns, film noir, and play adaptations. Nineteen actors appearing in Zinnemann's films received Academy Award nominations for their performances: among that number are Frank Sinatra, Audrey Hepburn, Glynis Johns, Paul Scofield, Robert Shaw, Wendy Hiller, Jason Robards, Vanessa Redgrave, Jane Fonda, Gary Cooper and Maximilian Schell. Zinnemann's 1950 film The Men is noted for giving Marlon Brando his first screen role.

Zinnemann enjoyed an outstanding career spanning six decades, during which he directed 22 features, 19 short subjects and won four Oscars. Perhaps his best-known work is High Noon (1952), one of the first 25 American film classics chosen in 1989 for the National Film Registry. With its psychological and moral examinations of its lawman hero, played by Gary Cooper, its allegorical political commentary (on McCarthy-era witch-hunting) and its innovative chronology whereby screen time approximated the tense 80-minute countdown to the confrontational hour, High Noon shattered the mould of the formulaic shoot-‘em-up western.

The director's other eminent films, all compelling dramas of lone and principled individuals tested by tragic events, include From Here to Eternity (1953); The Nun's Story (1959); A Man For All Seasons (1966); and Julia (1977). Regarded as a consummate craftsman, Zinnemann traditionally endowed his work with meticulous attention to detail, an intuitive gift for brilliant casting and a preoccupation with the moral dilemmas of his characters.

Zinnemann's penchant for realism and authenticity is evident in his first feature The Wave (1935), shot on location in Mexico with mostly non-professional actors recruited among the locals, which is one of the earliest examples of realism in narrative film. Earlier in the decade, in fact, Zinnemann had worked with documentarian Robert Flaherty, an association he considered "the most important event of my professional life".

His adaptation of The Seventh Cross, though filmed entirely on the MGM backlot, captured the essence of the Anna Seghers novel by realistic use of refugee German actors in even the smallest roles.

The filmmaker also used authentic locales and extras in The Search (1948), which won an Oscar for screenwriting and secured his position in the Hollywood establishment, a vivid drama of World War II aftermath in Berlin that drew on Zinnemann's skills as both documentarian and dramatist. Shot in war-ravaged Germany, the film stars Montgomery Clift in his screen debut as a GI who cares for a lost Czech boy traumatised by the war. In the critically acclaimed The Men (1950), starring newcomer Marlon Brando as a paraplegic war veteran, Zinnemann filmed many scenes in a California hospital where real patients served as extras.

Besides Clift and Brando, other Zinnemann discoveries included Pier Angeli and John Ericson, who co-starred in Teresa (1951), with Rod Steiger and Ralph Meeker debuting in secondary roles. And in Oklahoma! (1955), Zinnemann's version of the Rodgers and Hammerstein musical, the wide screen format Todd-AO made its debut, as did the film's young star Shirley Jones.

Zinnemann's casting choices were often as daring as they were judicious. For his screen adaptation of the play The Member of the Wedding (1952), Zinnemann chose the 26-year-old Julie Harris as the film's 12-year-old protagonist, although she had created the role on Broadway just as the two other leading actors, Ethel Waters and Brandon De Wilde, had. In From Here to Eternity (1953), he cast Frank Sinatra, who was at the lowest point of his popularity. As the likable loser Maggio, Sinatra won an Oscar for Best Supporting Actor. From Here to Eternity also featured Deborah Kerr, best known for prim and proper roles, as a philandering Army wife. And Audrey Hepburn, previously cast in delightful comedic roles, gave the performance of her career as the anguished Sister Luke in the highly acclaimed The Nun's Story.

Throughout his career Zinnemann favoured a protagonist morally impelled to act heroically in defence of his or her beliefs. Hepburn in The Nun's Story and Cooper in High Noon, determined to confront savage outlaws hungry for revenge, are two other prominent examples. Paul Scofield as Sir Thomas More in A Man For All Seasons (1966) gave a brilliant portrayal of a man driven by conscience to his ultimate fate.

A variation on that theme is found in The Seventh Cross, in which the central character -- an escaped prisoner played by Spencer Tracy -- is comparatively passive and fatalistic. He is, however, the subject of heroic assistance from anti-Nazi Germans. In a sense, the protagonist of the movie is not the Tracy characer but a humble German worker played by Hume Cronyn, who changes from Nazi sympathizer to active opponent of the regime as he aids Tracy.