On this day in 1963, an elderly Buddhist monk named Thich Quang Duc climbed from a car stopped at a busy intersection in Saigon. He sat down and crossed his legs as another monk poured gasoline over him and a third lit him on fire. Quang Duc began praying as flames engulfed his body. As he burned, passersby prostrated themselves before this horrifying spectacle of devotion. Quang Duc’s body finally toppled over, his flesh incinerated, leaving only his heart behind.

Quand Duc chose to immolate himself to protest Ngo Dinh Diem’s — the United States’s handpicked dictator in Vietnam — oppression of the nation’s Buddhist population. A bit more than a month earlier, as Buddhists in Hué readied to celebrate the Buddha’s birthday, a local factotum and Diem loyalist had refused to allow them to gather. Several thousand Buddhists then took to the streets for a peaceful protest. Police fired on the crowd. Nine people were killed in the melee.

Buddhists mounted more protests in the following weeks, demanding that Diem punish the officials responsible for the killings. Arrogant and out of his depth, Diem, a Catholic, vacillated between ignoring their entreaties and blaming the entire controversy on the Vietcong. Buddhists countered Diem’s intransigence with a campaign of demonstrations and propaganda: public rallies, high-profile hunger strikes, and coordinated interviews with foreign journalists. Tri Quang, one of the uprising’s leaders, suggested to American officials that, “The United States must either make Diem reform or get rid of him. If not, the situation will degenerate, and you worthy gentlemen will suffer most. You are responsible for the present trouble because you back Diem and his government of ignoramuses.”

True to form, those ignoramuses ignored pressure from Washington as well. It was against that backdrop that Quang Duc killed himself, generating international outrage. Newspapers worldwide published stories headed by a stark image of the immolation. Buddhists had tipped off an AP photographer, Malcolm Brown, about their plans. At the event itself, they handed out biographical sketches of Quang Duc, revealing that he had been sixty-six years old at the time of his death. His last words were a plea to Diem for compassion and religious toleration.

Instead, the Diem administration replied with scorn and crackdowns. As police raided Buddhist temples, Madame Nhu, Diem’s sister-in-law, referred to Quang Duc’s death as a “barbecue”. Less than six months later, a coup — if not supported by the CIA then certainly tolerated by the Agency — toppled Diem’s government. He and his brother, Ngo Dinh Nhu, were killed. Madame Nhu went into exile.