Those earlier immigrant roundups, in late 1919 and early 1920, are known in history books as the Palmer raids, after A. Mitchell Palmer, the attorney general who ordered them. He was aided in his efforts by a young Justice Department attorney named J. Edgar Hoover, whose experience helped lead to the emergence of the Federal Bureau of Investigation. President Woodrow Wilson set the table for the actions with his own harsh talk about subversives lurking within America’s borders, while a compliant judiciary gave the executive branch’s leaders every reason to think it wouldn’t stand in the way.