On November 7, 1919, raiding parties in twelve US cities, composed of federal agents and a motley assortment of local police and American Legionnaires, descended on the offices of the Union of Russian Workers, an organization of leftist immigrants. The raids coincided with the second anniversary of the Bolshevik Revolution and rounded up for arrest as many as one thousand people. Over the next two months, the onslaught continued, as leftists of various stripes were targeted all over the country. The largest assault came on January 2, 1920, with raids in some thirty-three cities aimed mainly at Communist groups. But this sustained attack on the Left would persist through the middle of February.

Dubbed the Palmer Raids after the man in charge of them, Attorney General A. Mitchell Palmer, this operation is widely regarded as the definitive event in the nation’s first great Red Scare. Coming only a few months after the Communist movement’s emergence in the United States, and capping off the most tumultuous year of social conflict the country would see all century, the raids were conducted with little concern for constitutional norms. All told, they resulted in the arrest of some ten thousand leftists, hundreds of whom were ultimately deported or criminally prosecuted.

The one-hundredth anniversary of this extraordinary series of events is an apt occasion to reflect on the Red Scare’s significance in US history. But in doing so it is crucial to go beyond the conventional wisdom and consider more carefully what the Red Scare was really about.