In Don Siegel’s 1958 film “The Lineup,” a cheerfully philosophical assassin patiently addresses a general misconception about his profession. “You don’t understand the criminal’s need for violence,” he says to a terrified law-abiding victim.The 25 films showcased in Film Forum’s four-week Siegel retrospective beginning today, demonstrate that, if there was anything the director-producer understood, it was that need.

Criminal, cop, or casualty, the characters in Siegel’s films occupied a fast-turning world of inescapable brutality. Laced with the irresistibly cinematic energy of human malice, Siegel films, such as “Hell Is for Heroes” (March 21), “Invasion of the Body Snatchers” (March 24-27), “Riot in Cell Block 11” (March 29-30), and “Dirty Harry” (April 7-13) defined American genre filmmaking with unparalleled precision and unyielding clarity.

Siegel’s filmmaking career began in the Warner Bros. editorial department, where he created most of the intersti tial montage sequences used to tighten and tune up Warner Bros. 1940s assembly-line cinema. It was Siegel’s breathless opening montage, for instance, that sold the dramatically necessary but geographically and politically ludicrous concept in “Casablanca” of an early WWII European refugee trail leading to Morocco.

All of Siegel’s feature films bear the stamp of this persuasive visual shorthand. A quick insert of a cowboy leaping into frame as he runs for cover in “Duel at Silver Creek” (April 24), a panning zoom up Dirty Harry’s gun barrel to Harry’s smiling face, Dana Wynter’s emotionless post-cat nap close-up in “Invasion of the Body Snatchers” – these dynamic and lucid moments linger in the mind like music.

A Siegel protagonist may have been dishonest (Richard Widmark’s “Madigan,” April 5-6), insane (Mickey Rooney in the ultra-rare “Baby Face Nelson,” March 30), sociopathic (Steve McQueen in “Hell Is for Heroes,” March 21), or incarcerated (the cons of “Riot” and “Escape From Alcatraz,” April 2-3), but that didn’t stop him from getting the job done as intelligently as circumstances permitted.

The apotheosis of these pragmatist heroes is Walter Matthau’s “Charley Varrick” (playing Friday through Sunday).This spectacularly brisk,gorgeously photographed 1973 film was perhaps the director’s most personal work. Varrick,the “last of the independents,” had a colorful flair for survival that mirrored the then 61-year-old Siegel’s Hollywood longevity.”Charley Varrick” has been particularly ill-served on home video (the DVD issue is panned and scanned). For 1970s crime movie aficionados, Film Forum’s new 35 mm CinemaScope print is an answered prayer.

Like Varrick and his doomed younger partner (played by the underrated Andy Robinson), Siegel heroes often came in ersatz father-son sets. Siegel himself was a generous cultivator of young talent. He gave Sam Peckinpah his first film job and opened his door to British horror director Michael Reeves. John Cassavetes once described Siegel as his “West Coast mother.” Siegel’s “The Killers” (March 31-April 1) ended Cassavetes’s two-year unofficial Hollywood house arrest for punching out producer Stanley Kramer.

Siegel’s most storied collaboration was with Clint Eastwood. Brought together for Universal’s “Coogan’s Bluff” (April 5-6), Mr. Eastwood gave Siegel enough box office clout to avoid languishing in television. In return, Siegel lent Mr. Eastwood his director’s chair. Temporarily felled by the flu during the grueling month-long location shoot of “Dirty Harry,” the director generously abdicated to his star for two days. Harry’s memorable negotiation with a potential suicide marked Mr. Eastwood’s uncredited directorial debut. Mr. Eastwood returned the favor by casting Siegel in a small role in the star’s full-length directorial debut, “Play Misty for Me.” His 1992 film “Unforgiven,” released a year after Siegel’s death, bears a split dedication to “Don and Sergio.”

“Don talks like an actor, [he] loves to be around them,” recalled “Cell Block 11” co-heavy Neville Brand. A Royal Academy of Dramatic Arts trainee, Siegel shepherded John Wayne through his best non-Ford or Hawks performance in “The Shootist” (April 2-3) and gave Elvis Presley his strongest (nearly songless) role in “Flaming Star” (March 28). Henry Fonda and Richard Widmark’s tacit and uneasy chance meeting in “Madigan” is as minutely observed as Andy Robinson’s liquor store sneak attack in “Harry” is volcanically real and graphic.

In every Siegel picture, location and stakes mesh with an honesty and lack of audacity that is missing from American action films today. Consider the closing coda of “Dirty Harry.”The camera slowly zooms back. For a moment it seems like we may gain high enough ground to sort out Harry’s decidedly gray morality. But as the credits begin, the frame stops, leaving Harry to cope with the results of his actions inside a lonely maze of Oakland highways. If the film were made today, the camera would continue zooming back out until we’d left earth orbit’s and escaped the gravity of loss and hope – two ephemeral themes that were as real and plentiful as bullets in Siegel’s films.

Until April 13 (209 W. Houston Street, between Sixth Avenue and Varick Street, 212-727-8110).