The book is full of high-stakes episodes in which the right decision is not clear. The “powerful sword” of the strike gets special attention throughout. In the 1970s, there were nearly 300 large strikes — comprising at least 1,000 workers — every year. After Reagan, that number plummeted to under 60. From 2008 to 2018, the average number was just 13.

The 1936-37 General Motors sit-down strikes by the United Automobile Workers, which led to the unionization of the auto industry — and widespread unionization across other sectors — get a heart-pounding chapter, where union leadership is constantly struggling with its own membership, the membership itself is divided and public opinion shifts perilously. At one of many critical moments, a change in wind literally changes the outcome of an encounter with the police: Tear gas directed at strikers and their supporters flies back, forcing a police retreat. The G.M. workers’ spirits go up and down, they make strategies that work better than planned and others that are foiled altogether. There are several times when it looks as if they will fail entirely, and could be killed doing so.

Just because history is not foreordained does not mean it is random, however. One powerful lesson of the U.A.W. sit-down is the importance of radical vision and the bravery of a few workers; another is that elected and appointed officials can make a huge difference in private labor disputes. At one point, Secretary of Labor Frances Perkins yells over the phone at the head of G.M.: “You are a scoundrel and a skunk, Mr. Sloan! … You don’t deserve to be counted among decent men! … You have betrayed the men who work for you.” Alfred Sloan apparently retorted: “You can’t talk like that to me! I’m worth $70 million, and I made it all myself!”

With the breaking of the air traffic controllers’ strike in 1981, the Reagan years are generally understood as the tipping point in labor history. It would be tempting to write about that strike through the lens of Reagan’s ideology alone or, alternatively, to blame the strikers for their defeat. But Greenhouse gives the events leading up to the strike the respect and context they deserve, making it possible even for a reader who knows exactly how it turns out to hope that things might go differently, because the world from inside the minds of the strikers seems so coherent.

Great nonfiction requires great characters, and Greenhouse has the gift of portraiture. He is able to draw a complex, human portrait of a worker with a minimum of words, making the reader greedy for more details, not just about the policies but about the people. And he has both the newspaper writer’s ability to find the one or two individuals whose personal stories exemplify a larger point, and the historian’s ability to make what has already happened seem unlikely. He is skilled at homing in on the moments of the highest uncertainty, and transforming them into stories with quick and destabilizing twists and turns.

Greenhouse may be a great advocate for unions, but he has no patience for union insiders who have grown used to internal power and external weakness, who ask for too little and focus too much attention on strategies designed to minimize damage. George Meany, the longtime head of the A.F.L.-C.I.O., comes in for special scorn, standing for insular, uninspired, bureaucratic leadership. Meany once said: “I used to worry about the membership, about the size of membership. But quite a few years ago I just stopped worrying about it, because to me it doesn’t make any difference.” He added, “Why should we worry about organizing people who do not appear to want to be organized?” Union officials during the 1970s may not have been as direct, but they had the same view, and it showed up in their spending: While in the 1930s, unions spent over half their money on organizing, in the 1970s, many unions spent under 5 percent.

But Greenhouse’s greatest anger is for the large companies — and their Wall Street owners — that have no human connection to the workplace and that are pushing the limits with new tactics to demoralize workers and strip them of their power and dignity. When a unionization flier was found in a Walmart bathroom, the company sent in a SWAT team the next day to nip empowerment in the bud. Companies also buy up the airwaves: In 2017, Boeing ran 485 television ads aimed at 3,000 workers during a unionization drive.