Martin Luther King Jr.'s 1963 Letter from a Birmingham Jail defends nonviolent direct action against racial segregation. Written from jail, he explains his presence in Birmingham as an invited leader of the Southern Christian Leadership Conference. King outlines a four-step campaign: fact collection, negotiation, self-purification, and direct action.

King argues Birmingham was the most segregated U.S. city, with brutal police brutality and broken merchant promises. He frames nonviolent direct action as a way to create constructive tension, forcing a community to confront injustice. This method aims to dramatize issues until negotiation becomes unavoidable, countering claims of being an "outside agitator."

The letter remains a foundational text on civil resistance, detailing how strategic pressure can break systemic barriers. Its principles of organized, disciplined protest continue to influence modern social movements. King’s response to clergy criticism underscores the moral urgency of acting against injustice, regardless of timing.