Ludlow, Colorado, 1914: eleven thousand mine workers had been on strike for seven months against John D. Rockefeller’s Colorado Fuel and Iron Company, protesting low pay and dangerous conditions. They were overwhelmingly immigrants, from Greece, Italy, Mexico, Croatia, Austria, Montenegro, and elsewhere, speaking at least twenty-two different languages. The company had evicted them from their homes, so they were camped out in the snow in a tent colony, frozen and starving.

The morning of April 20, the Colorado National Guard, called in at Rockefeller’s behest, opened fire from a machine gun set up on a hill above the strikers’ homes, then rushed in to burn down the whole colony. “The soldiers and mine guards tried to kill everybody, anything they saw move, even a dog, they shot at,” one witness reported. The Guard killed three unarmed strikers who were holding aloft white flags, including their Greek leader, Louis Tikas, among others. It used fuel oil to incinerate three women and eleven children huddling in cellars.

What became known as the Ludlow Massacre offers a sharp reminder of the long and vicious history of superrich employers using the National Guard to break strikes, especially between 1877 and World War I. As we recoil with horror at President Donald Trump sending the National Guard and the Marines into Los Angeles to repress pro-immigrant demonstrations, discussions of the National Guard’s history have focused either on the authority of a president to deploy it against the will of the governor or its role during the civil rights era.