Rev. Martin Luther King is widely renowned for being on the forefront of the fight for civil rights, a movement that contributed to the implementation of directives such as the Civil Rights Act and the Voting Rights Act. He’s acknowledged by historians and modern-day activists alike for his distinctive leadership and his fiery speeches that invigorated millions of people at once.

“He was trying to get us where we wouldn’t have to sit on the back of the bus no more,” Renee Pernell, a protester who marched with Martin Luther King in Birmingham in 1963, said. “We thought he was very brave to go to jail for something that he was trying to do for not just Black people, but for everybody. He was a good speaker, and a great man. He just wanted everybody to get along.”

King’s delivery of “I Have a Dream” at the 1963 March on Washington is undoubtedly his most known speech–it remains widely studied (and quoted) today, and over a quarter million people attended the March on Washington itself. But in April of 1967–50 years ago–King delivered another high-profile speech at the Riverside Church in New York City, and with his speech, contributed to another movement: the antiwar campaign.

In his speech, King denounced the Vietnam War and how American involvement in the war was a betrayal of traditional values–that it evoked imperialistic objectives and resulted in the rising death toll of American and Vietnamese soldiers in combat.

“The war in Vietnam is but a symptom of a far deeper malady within the American spirit,” King said in his speech at the church. “A nation that continues year after year to spend more money on military defense than on programs of social uplift is approaching spiritual death.”

Luther’s speech, which was delivered at a time before mass protests and opposition to the war itself were common, was controversial, even amongst his civil rights allies. Newspaper publications such as the New York Times viewed King’s outcry against the war as an “error,” and President Lyndon B. Johnson–a staunch supporter of King’s goals with the civil rights movement–was the figure behind the continuation and escalation of the war.

Despite the opposition to King’s viewpoints, many activists–particularly everyday citizens–dissented against the Vietnam War as well. Antiwar protests defined the late sixties and early seventies, taking place from government mansions to Pennsylvania Avenue and even across the globe.

The most-attended and most-broadcasted manifestation of the movement was the Vietnam War protest of 1969, a rally which over half a million people attended to oppose US participation in the Vietnam War. This march on Washington was just one of many demonstrations that spanned the nation in the following years, all contributing to the most heated antiwar movement in American history. These protests did not end American involvement in the war– which only terminated after the fall of Saigon in 1975– but they served as proof of the strength of the antiwar movement and how it consisted of people across all different levels of society.