“There are two types of laws, just and unjust,” wrote Dr. Martin Luther King Jr. from jail on Easter weekend, 1963. “One has a moral responsibility to disobey unjust laws.” St. Thomas Aquinas would not have disagreed. The image burnished into national memory is the Dr. King of “I Have a Dream,” delivered more than 50 years ago in Washington, D.C. So it’s hard to conjure up the 34-year-old in a narrow cell in Birmingham City Jail, hunkered down alone at sunset, using the margins of newspapers and the backs of legal papers to articulate the philosophical foundation of the Civil Rights Movement.

Letter From Birmingham City Jail,” now considered a classic of world literature, was crafted as a response to eight local white clergymen who had denounced Dr. King’s nonviolent protest in the Birmingham News, demanding an end to the demonstrations for desegregation of lunch counters, restrooms and stores. Dr. King’s letter had to be smuggled out of the jail in installments by his attorneys, arriving thought by thought at the Southern Christian Leadership Conference’s makeshift nerve center at the Gaston Motel. An intensely disciplined Christian, Dr. King was able to mold a modern manifesto of nonviolent resistance out of the teachings of Jesus and Gandhi.

Throughout the 1960s the very word “Birmingham” conjured up haunting images of church bombings and the brutality of Eugene “Bull” Connor’s police, snarling dogs and high-powered fire hoses. When King spent his nine days in the Birmingham jail, it was one of the most rigidly segregated cities in the South, although African Americans made up 40 percent of the population. As Harrison Salisbury wrote in The New York Times, “the streets, the water supply, and the sewer system” were the only public facilities shared by both races. Yet by the time Dr. King was murdered in Memphis five years later, his philosophy had triumphed and Jim Crow laws had been smashed. “Letter From Birmingham City Jail” would eventually be translated into more than 40 languages.

Thanks to Dr. King’s letter, “Birmingham” had become a clarion call for action by the anti-apartheid movement in South Africa, especially in the 1980s, when the international outcry to free Nelson Mandela reached its zenith. Archbishop Desmond Tutu quoted the letter in his sermons, Jamaican reggae singer Bob Marley kept the text with him for good luck, and Ghana’s Prime Minister Kwame Nkrumah’s children chanted from it as though Dr. King’s text were a holy writ. During the Cold War, Czechoslovakia’s Charter 77, Poland’s Solidarity and East Germany’s Pastors’ Movement all had “Letter From Birmingham City Jail” translated and disseminated to the masses via the underground.

Just as Dr. King had been inspired by Henry David Thoreau’s essay “Civil Disobedience,” written in a Massachusetts jail to protest the Mexican-American War, a new generation of the globally oppressed embraced the letter as a source of courage and inspiration. Segregation and apartheid were supported by clearly unjust laws—because they distorted the soul and damaged the psyche. Dr. King’s remedy: nonviolent direct action, the only spiritually valid way to bring gross injustice to the surface, where it could be seen and dealt with.

In Jerusalem in 1983, Mubarak Awad, an American-educated clinical psychologist, translated the letter for Palestinians to use in their workshops to teach students about nonviolent struggle. When a Chinese student stood in front of a tank in Tiananmen Square on June 4, 1989, unflinching in his democratic convictions, he was symbolically acting upon the teachings of Dr. King as elucidated in his fearless Birmingham letter.

Argentinian human rights activist Adolfo PĂ©rez Esquivel, the 1980 Nobel Peace Prize winner, was inspired in part by King’s letter to create Servicio Paz y Justicia, a Latin American organization that documented the tragedy of the desaparecidos. Today one would be hard-pressed to find an African novelist or poet, including Chinua Achebe and Wole Soyinka, who had not been spurred to denounce authoritarianism by King’s notion that it was morally essential to become a bold protagonist for justice. Even conservative Republican William J. Bennett included “Letter From Birmingham City Jail” in his Book of Virtues.

The universal appeal of Dr. King’s letter lies in the hope it provides the disinherited of the earth, the millions of voiceless poor who populate the planet from the garbage dumps of Calcutta to the AIDS villages of Haiti. His letter describes the “shameful humiliation” and “inexpressible cruelties” of American slavery, and just as Dr. King was forced to reduce his sacred thoughts to the profane words of the newspaper in order to triumph over injustice, African Americans would win their freedom someday because “the sacred heritage of our nations and eternal will of God are embodied in our echoing demands.”

The National Park Service has designated Sweet Auburn Avenue in Atlanta, where Dr. King lived and is buried, a historic district. Banks, businesses and government offices are closed to honor the civil rights martyr every January. But the living tribute to Dr. King, the one that would have delighted him most, is the impact that his “Letter From Birmingham City Jail” has had on three generations of international freedom fighters.

These pages of poetry and justice now stand as one of the supreme 20th-century instruction manuals of self-help on how Davids can stand up to Goliaths without spilling blood. As an eternal statement that resonates hope in the valleys of despair, “Letter From Birmingham City Jail” is unrivaled, an American document as distinctive as the Declaration of Independence or the Emancipation Proclamation.

This article was written by Douglas Brinkley and originally published in August 2003 issue of American History Magazine. For more great articles be sure to subscribe to American History magazine today!