Rustin, Dr. King’s mentor in nonviolence, was in many ways a force of nature when it came to fighting injustice. But the man who could tame the police — and who many fellow activists thought would become the “American Gandhi” — had an Achilles’ heel, at least given the time in which he lived. Rustin was not only a Black man, he was a gay man. And with the march just weeks away, some of the most powerful men in Washington seized on that fact in a last-ditch effort to take down its formidable organizer and cripple the mass demonstration.

The March on Washington has become an event of enormous magnitude in American history. It was the day that consolidated the gains of the nonviolent demonstrations in places like Montgomery and Birmingham, helped prompt the landmark Civil Rights Act of 1964 and launched Dr. King to national fame. Such a large-scale civil rights demonstration was unprecedented, though, and risky. Any disturbance of the peace or outbreak of violence among the more than 200,000 people gathered near the Lincoln Memorial that day would have been the big story in the newspapers and history books, not Dr. King’s speech.

Pulling off such an event without a hitch took a monumental effort, and a singular person to do the pulling. An avid proponent and practitioner of Gandhian nonviolence, Rustin had worked in the pacifist movement for decades and, more than any other person, was responsible for injecting the principles of nonviolent resistance into the Black freedom struggle in America. Rustin had less than two months to pull the March together, and he left nothing to chance, from the number of first-aid stations needed for a quarter of a million people to the number of toilets. In addition to training police officers, he booked buses, vetted speeches, ordered food and, most important, tried to stay under the radar.

Why? Because as talented an organizer as Rustin was, his fellow civil rights activists had taken an enormous risk in putting him in charge. Rustin made no effort to hide his sexuality, which many leaders in the movement (who were largely ministers) considered immoral. In an era in which homosexuality was illegal in most states, Rustin had been labeled a sex offender a decade earlier when police found him with two white men in a parked car in Pasadena, California. An influential adviser to Dr. King in the early stages of the civil rights movement, Rustin had been forced to resign from the Southern Christian Leadership Conference in 1960 when Adam Clayton Powell, a Harlem congressman, threatened to spread the rumor that Rustin and King were lovers.

By early August, says Rustin biographer John D’Emilio, Rustin’s role in organizing the March was becoming increasingly public. At one point, he was described in The Washington Post as “Mr. March on Washington.” Rustin’s cover was blown, and he became a target for opponents of the march, including segregationist legislators and the highest-ranking members of the intelligence community. “It aroused the anger and frustration of FBI Director J. Edgar Hoover, who was very hostile to Black protest and the civil rights movement,” says D’Emilio.

Hoover ordered his FBI to gather information about Rustin’s sexuality and past — and delivered it to Strom Thurmond, a white segregationist senator from South Carolina. Just two weeks before the March, Thurmond took to the floor of the Senate, where he denounced Rustin in a diatribe that takes up eight pages in the Congressional Record, which included labeling him a convicted “sex pervert.”

But the efforts to impugn Rustin and sandbag the march failed: This time, civil rights leaders rallied to the embattled activist’s defense so that he didn’t lose his role as organizer. For Rustin, it marked a turning point in how he was treated by his fellow activists. He later called the attack “the best thing [Thurmond] could have done for me.” As a result, Rustin also became the most visible homosexual in America. And, a week after the march, after Rustin personally ensured there was not a single scrap of trash or paper left on the Washington Mall, his picture appeared on the cover of Life magazine. In it, Rustin stands at the feet of the large marble Lincoln — a man in the shadow of a giant of history, but a towering figure in his own right.