In January 1917, John Hays Hammond, a balding, mustachioed mining engineer, appeared before the convention of the National Civic Federation, an alliance of business leaders and conservative unions, to deliver a stark warning: the country’s workers and farmers were dead set against entering World War I.

“Some influence or combination of influences has certainly brought about a weakening of the patriotic sprit in this country,” Hammond lamented. “We find that neither the workingmen nor the farmers . . . are taking any part or interest in . . . movements for national preparedness.”

By the following year, however, a combination of government propaganda, repression, and wartime hysteria had shoved anti-war views out of the political mainstream. President Woodrow Wilson’s declaration of war in April 1917 was the opening shot, and a fusillade of jingoism soon followed: suppression of radical publications, sacking of dissident organizations’ offices, tarring and feathering of war opponents, hyperpatriotic displays at sporting events, a $50 state bounty for draft dodgers, government-financed cartoons comparing Germans to barbarous, rampaging animals.