Thousands are expected this week in the forested hills of southern West Virginia to commemorate the 100th anniversary of the Battle of Blair Mountain—a key conflict in labor history.

In the late summer of 1921, at least 7,000 coal miners affiliated with the United Mine Workers of America (UMWA) fought for their rights and their livelihoods in a weeklong fight against a private army that was raised by the coal companies and supported by the National Guard and the U.S. Army Air Force. The battle was the climax of two decades of low-intensity warfare across the coalfields of Appalachia, and it remains the largest battle on U.S. soil since the end of the Civil War.

The battle is also a stark reminder of the importance of protecting workers’ right to organize. It’s not simply about balancing the economic scales; it’s about power. When workers do not have power—when they have no voice in their workplace and no voice in how the nation is governed—exploitation and violence by the state are the inevitable result.

Today, workers still face a lack of power. A great way to empower workers would be through passing the Protecting the Right to Organize (PRO) Act, which is currently being considered by Congress and was renamed after former UMWA President Richard Trumka following his passing earlier this month. The story of the Battle of Blair Mountain demonstrates how, a hundred years on, workers are at the mercy of the powerful unless they have unions and power of their own.

The immediate origin of the battle was the conflict in Mingo County, West Virginia. Fighting during the previous year in Mingo County, including shootouts, ambushes, and bombings, was the basis for John Sayles’s 1987 film, Matewan. By the summer of 1921, the governor had imposed martial law when asked by the mine companies, as the historian James Green details in his 2015 book, The Devil Is Here in These Hills: West Virginia’s Coal Miners and Their Battle for Freedom. 

That isn’t an exaggerated description of the companies’ power. In many mining regions in the late 19th and early 20th centuries, mine companies for all practical purposes were the government. Seven years before the Battle of Blair Mountain, J.D. Rockefeller’s Colorado Fuel and Iron Company paid the salaries of the National Guardsmen who opened fire on a tent city of strikers and their families in Ludlow, Colorado. Sixty-six people were killed, including at least 11 children, as the tent city was set ablaze. No one was charged with or convicted of any crime in connection with the massacre.

In West Virginia in 1921, the mine companies raised a private army of some 2,000 men, many of them World War I veterans, and imprisoned union leaders in Mingo County. The Baldwin-Felts Detective Agency, hired by the Stone Mountain Coal Company and other coal mine owners to facilitate union busting, helped organize the private army.

There is a clear line to be drawn from the violent tactics of Baldwin-Felts to the smoother, legalistic strategies of present-day law firms like Morgan Lewis, which advised Amazon in its efforts to defeat the unionization effort in Bessemer, Alabama, earlier this year. (A new election is likely to be ordered based on Unfair Labor Practices committed by the company.) Corporations have always shown a willingness to spend money like water to suppress worker organizing.