On November 25, 1960, a car carrying three Dominican political dissidents, the Mirabal sisters, is stopped as they travel to visit a prison where two of their husbands are being held. Members of the Dominican Republic’s secret police, including the alleged “right-hand man” of dictator Rafael Trujillo, beat the sisters and their driver to death, placing their bodies in the car and pushing it over a cliff in an attempt to make the murders look like an accident. The cover-up fools nobody, and the Mirabal sisters become martyrs of the Dominican resistance. Within a year, Trujillo will also be killed in a roadside ambush.

Patria, Minerva and María Teresa Mirabal came from a well-off family in the Dominican Republic’s central Cibao region. Although their parents disliked Trujillo, who seized power in 1930, they discouraged their daughters from getting involved with the resistance. While the second sister, Dedé, heeded this advice, the other three became involved with the resistance, along with their husbands. In the case of Minerva, the first woman to graduate from law school in the Dominical Republic, it was personal. After she rejected Trujillo’s advances at a party, she was repeatedly harassed by his forces and even stripped of her law license.

Trujillo’s regime had been brutal from the start—he committed many atrocities, including a massacre of tens of thousands of Haitians near their shared border in 1937—but cracked down even harder in the wake of the Cuban Revolution in 1959, which energized the Dominican resistance. After a number of dissidents were tortured and killed by Trujillo’s regime on June 14, 1959, the “Butterflies,” as the Mirabal sisters were known, helped form and lead the 14th of June Movement, distributing pamphlets and attempting to educate the public about Trujillo’s crimes. Along with their husbands, they were quickly arrested by the secret police, but the sisters were soon released.

Believing they had finally been granted permission to visit the two of their husbands who remained imprisoned, the three sisters were instead ambushed and murdered on this day in 1960. In the years after Trujillo’s fall, it was confirmed that the order to kill them had come from the dictator himself. Although his countless atrocities were widely known in the DR, the murder of the Butterflies struck a particular chord. Despite its brutality, Trujillo’s government made much of its allegedly compassionate and progressive attitude toward women, granting women the right to vote in 1942 and sending one of the first female delegates ever to the United Nations.

The cold-blooded murder of three well-known sisters underscored the raw violence that formed the true basis of Trujillo’s power. Although their martyrdom did not directly bring about his fall, the Mirabal sisters’ actions and their assassination hold an important place in modern Dominican history and the story of how the nation finally broke free of the Trujillo regime.