The American communist movement was born in the summer of 1919, when the left wing of the Socialist Party split into the Communist Party of America and the Communist Labor Party — and the federal government attacked it almost at birth. In November 1919 and January 1920, Attorney General A. Mitchell Palmer and his young Radical Division chief J. Edgar Hoover directed coordinated raids in dozens of cities, arresting as many as ten thousand radicals, most without warrants, holding them incommunicado in overcrowded detention pens.
Hundreds of foreign-born members were deported — 249 on the Buford, the "Soviet Ark," in December 1919 — while citizens faced state sedition and criminal-anarchy prosecutions, including CLP founder Benjamin Gitlow, whose case reached the Supreme Court. The raids drove the movement underground for years and established the deportation of immigrant radicals as a permanent weapon of American politics.