"You don't assign him to murder cases, you just turn him loose." So began the ad campaign for one of Clint Eastwood's most enduring movie characters, Dirty Harry Callahan.

In the middle of the 1960s, though, Eastwood was something of a Hollywood pariah having just barely escaped his connection to the TV series Rawhide only to find few opportunities to ply his craft on the big screen. Turning to Italian producers and writer-director Sergio Leone who hired him to play the lead in a group of so-called spaghetti westerns, Eastwood flew to Italy and originated the legendary role of The Man With No Name. In so doing he created one of his most enduring movie characters complete with a certain Christ-like mythology and a number of superhuman qualities.

By the late '60s Eastwood was able to return to America as one of the country's pre-eminent stars. After the release of The Good, the Bad, and the Ugly, his heroic turn as a western hero, he was successfully translated from being a TV star into a global movie star of nearly unprecedented adulation. His salary soared, his popularity among male and female moviegoers alike grew steadily and his on-screen persona was cemented behind the squint of steely blue eyes, a fit body and dialogue delivered always with a touch of indifference to authority in all its forms.

With the script of Dirty Harry making the rounds in Hollywood in 1970 the project's producer-director, Don Siegel, originally intended the part for Frank Sinatra. After he refused it an offer was extended to John Wayne and then to Paul Newman before finally being handed to Clint Eastwood who accepted the role.

The movie tells the story of San Francisco police detective Harry Callahan who is an outsider in his profession as much for losing partners as for his martial means at corralling criminals. Into his midst comes a serial killer called Scorpio (Andrew Robinson) who randomly targets victims throughout the city, eventually ransoming a kidnapped teenage girl who he brutally rapes and suffocates in an underground tomb.

Harry is assigned to the case and determines Scorpio's identity but is unable to make an arrest due to botched investigative procedures. Suspended from the case, Harry continues pursuing Scorpio until he renders final justice and shoots the crazed murderer with a repeated line of dialogue about the power of .357 Magnum, "the most powerful handgun in the world."

American war hero and actor Audie Murphy was first approached to play the serial killer but was killed in a plane crash before he could accept the part let alone fulfill the commitment. The role was then given to Robinson who managed to turn the character into one of the screen's great bad guys.

By coincidence Robinson is also a committed pacifist so the part required terrific control due to his terror of guns and violence. During the shoot, in fact, Siegel shut down production for almost a week and hired a firearms expert to work with him continuously until he was realistically able to fire a gun without flinching or otherwise compromising the part with his off-screen beliefs.

Once released, Dirty Harry was celebrated among the more conservative elements in society and often times condemned in the more liberal population. Having been directed and edited for maximum visceral appeal it jolted all audience members and caused a flurry of excitement at the box office. It was one of the year's biggest hits and echoed what has retroactively seemed like the theme of 1971 in the collapse of traditional masculinity and an assault on civilized society.

It's a movie long on shots looking down gun barrels and otherwise devoted to Harry's pursuit of the psychotic serial killer rampaging unchecked through his city. San Francisco itself is thus significant as another character in the film with its hilly topography and coastal perch above the Pacific Ocean. Added to the location is a score with Led Zeppelin-esque riffs and jazz-inspired moments by Lalo Schifrin whose music pulses beneath the action and frames Harry as a modern cowboy caught in circumstances he's all but helpless to control.

Interestingly the film also provided Eastwood with an opportunity to assist long-time benefactor and mentor Don Siegel by filling in for certain directorial needs when Siegel became sick during production. Dirty Harry also saw the codification of Eastwood's Malpaso Company in partnership with Warner Bros. that has proved a long lasting partnership between his independent production company and a big studio distributor that has continued through many films into the present.

1971 was also the year of The French Connection with its maverick cop "Popeye" Doyle (Gene Hackman) running ragged and rough shod through the streets of New York City. An obvious parallel of individual law enforcers at odds with the prevailing system exists between Popeye and Harry along with a now long-standing idea about such outsiders are more effective at putting away criminals than any other kind of cop.

This very notion of a proto-criminal police force being the remedy for rising crime was not new to the 1970s. However, it was portrayed with particular conviction in movies of the day with a variety of stars and directors contributing to the cycle and included the likes of Al Pacino, Charles Bronson, Sidney Lumet and Tom Laughlin.

Consistent across all these cinematic visions of good cops caught in a system that rewards criminals with inconsistent punishment while restricting the police from doing their duty is an analogy about the political spectrum. Gone are the right wing ideals of an ethical state with its reliance on absolute governmental authority and individual responsibility. In its place are the relatively liberal values of universal humanism and cultural maintenance that promotes individual rights even while creating a circumstance for civil conflict and decay in the distinction between old and new values.

Created in the midst of these societal pressures loosely pared beneath the Republican and Democratic parties and the Depression-era and Baby Boom generation was the character of Dirty Harry. Loosely derived from the events surrounding the Zodiac Killer who was actively killing people in San Francisco at the time, Harry's story makes him a complex amalgam of political beliefs and ideological contradictions.

On the one hand he's a bullets-and-brains Republican hero with an absolute and incorruptible moral code of conduct in pursuit of the crazed Scorpio who manages to be connected to the peace movement within the film even though he's a serial killer. But Harry was also a malleable enough heroic figure to become a near counter-cultural symbol through subsequent sequels and refinements leading up through a fifth Dirty Harry movie, The Dead Pool. In each sequel he was seen resisting fascist bad cops in Magnum Force, a gang of domestic terrorist in The Enforcer and even contributing to the vigilante efforts of an avenging rape victim in Sudden Impact.

Each of these films in the Dirty Harry franchise managed to be crowd pleaser. Each film managed to make a pile of money and each film managed to convey the expanding place of Clint Eastwood in American movies leaving not doubt, finally, about the importance of his movie character's contribution to Hollywood.

Dirty Harry Callahan may be a dirty cop but he's dirty because the world is a criminal undertaking with evil people who need to be stopped.