Hey folks, I ended up writing an answer in response to this r/AskHistorians thread yesterday. The poster was asking about historical vignettes that they should discuss with a classroom full of union construction workers. Since I ended up writing quite a bit, I figured other people might want to read it. This just reflects close readings of a few books I’ve read for coursework, and touches upon some other things I know about the UAW and NYC labor through personal experience.
There are two cases that I think would be useful in thinking about labor movement militancy.
First, the industrial labor movement's strongest moments. The statistics tell a lot of this story - union membership exploded in the 1930s, as did the number of strikes. For instance, United Mine Workers' membership grew from 60,000 to 300,000 in the span of two months (in 1933), and the International Ladies Garment Workers Union quadrupled to 200,000 members between 1933 and 1934. The "standard story" is that the success of the labor movement followed organically from mass membership.
But the most important part of this story is the specific tactics facilitated by radical cadres. Indeed, at first, the growth in union membership was perceived by union leadership at best as unanticipated and at worst as a threat to their power. In the American Federation of Labor, for example, large craft union locals uneasily incorporated newly organized industrial members. These new members (e.g., auto workers) were more keen to strike than their craft union seniors, who had even personally worked to break strikes among their own memberships (see e.g. Michael Tighe and the Amalgamated Association of Iron, Steel, and Tin Workers). All of this is to say, just joining an existing union structure didn't mean that workers stood to gain much at all - and indeed, the upsurge of workers looking to unionize was met by existing institutional unions with a mix of bewilderment and apprehension.
The most important and militant tactic utilized during this period was the sit-down strike, and the nascent United Auto Workers union (affiliated w/ the CIO) was at the center of it. Sit-down strikes differ from other strikes in that it's not just a work stoppage, it's a physical prevention of replacement labor - if you're occupying the factory where cars get made, scabs can't come in to get things running again. In December 1936, following spontaneous strikes at GM plants in OH, KS, and GA, workers in Flint MI sat down in several plants on the line. Most Flint auto workers were not official union members at the time. The sit-down wave soon spread to Detroit, and then to states like Indiana and Ohio. Eventually, some 112,000 GM workers were idle, and GM was losing $2 million a day in sales. Police were set against the strikers, using tear gas and guns, and strikers returned fire with fire hoses, auto hinges, bottles, and rocks (see the Battle of the Running Bulls). Eventually, Michigan's governor was forced to intervene, who had been elected with the endorsement of the Michigan labor movement. He tried in vain to negotiate a truce. Then FDR also tried and failed to do the same. When a court ordered workers to leave the plants after more than a month of striking, workers basically told the governor to pound sand. Eventually, the National Guard were sent out, but were blocked by thousands of strike-supporters from nearby cities. Over 10,000 marchers circled the closed plant, carrying clubs, pipes, and so on. In this fraught context, FDR's Secretary of Labor was able to set up a meeting between the CIO, auto union leaders, and GM. The strikers won union recognition (their main demand). A similar sequence happened soon afterward in Chrysler plants.
In 1936, there were 48 sit-down strikes. In 1937, there were >500. The tactic spread to mines and even movie theaters. Who was organizing this militant wave of labor actions? It wasn't the AFL, the CIO, or the UAW. It was, some scholars argue, Communists: the Industrial Workers of the World, Trotskyists, and the Communist Party in particular with its Trade Union Educational League. We don't see sit-down strikes today because they were ruled illegal in 1939 (see the 1939 Supreme Court ruling in NLRB v. Fansteel Metallurgical Corp.). I'm going to cut the discussion short here, but basically, politicians moved to formally incorporate (and, I'd argue, defang) the labor movement via the National Labor Relations Board, delimiting "legal" and "illegal" strikes.
My main source for the above section is Piven and Cloward's Poor People's Movements, Chapter 3. Supporting texts include Goldfield's "Worker Insurgency, Radical Organization, and New Deal Labor Legislation" and Skocpol and Finegold's "Explaining New Deal Labor Policy," each published in the American Political Science Review. I recommend mining Piven and Cloward for primary sources and historical monographs.
The second case I want to look at is a non-industrial labor movement, since the recent resurgence of the American labor movement is decidedly non-industrial. By 2010, more than 400,000 care workers - mostly home health aides - had unionized, most of whom were women of color. This is a curious case, because this isn't an instance of mobilization against capitalists - these workers were working in labor markets created by the government, some of which actually began during the New Deal (nice continuity with the first case I discussed). This was basically an effort to get Black women "off the dole" and improve their wages through a project of professional distinction from nursing (around the same time, nurses were strongly protesting the idea of being sent into private homes to practice).
Fast forward several decades, and this is a robust labor sector in e.g. New York City. Yet legally speaking, these care workers are not government employees. They're more like independent contractors, which means they're excluded from the 1938 Fair Labor Standards Act. This also means it's unclear who their employer is, if, say, they wanted to get a union contract. A union-lookalike campaign develops in the 1970s at the intersection of the Service Employees International Union and civil rights organizations like the Urban League. They organized home care workers agency by agency in a campaign against New York City's effort to restructure these agencies to a "vendor" system (basically, privatizing service provision). SEIU 32BJ filed a ton of NLRB petitions, not unlike how the Starbucks union is going about things today. But they had to use a very different strategy, since elders in need of medical care could be seen as a victim of labor organizing. Instead of casting patients/clients as enemies, care workers and organizers worked to incorporate them into the movement as beneficiaries in the fight against welfare cuts. The logic was, better work conditions for care workers benefits the recipients of care, too.
A similar campaign was also mounted in Chicago - SEIU Local 880 - in the wake of Reagan's firing of air traffic controllers. Instead of trying to get lists of care worker employees to organize from government agencies, organizers instead went to bus stops, hallways of housing projects, and hood streets to find the workers. Through this ground-game style work, organizers identified highly motivated rank and file organizers who became the core of that local's actions. They had regular events to build social ties among organizers (speakouts, honk-ins, monthly meetings with political education) and would show up to the relevant government office and deliver testimonials of disrespect and mistreatment. All of this happened under a right-wing NLRB - the "legal" methods were not going to be sufficient to win. Combining a militant strike threat with organized patients' threat to move their dollars to another agency, Chicago care workers were able to secure their first contract.
The tragic part of this story is that none of the locals detailed here remain in their strong forms today. The rank and file forward organizing strategy has all but completely disappeared. Union democracy and participatory practices fell off, and in line with the "business union" format, militancy gives way to stability.
Main source for the above section is Boris and Klein's "Caring for America," primarily chapters 5 and 6.
I presented these two cases so you can see that "militancy" can mean literally marching around a sit-down strike with pipes to defend it, or it can mean creative approaches to rank-and-file organizing that go beyond what institutional union organizers are willing or able to facilitate. The role of the United Auto Workers in particular is fascinating here, since they are an archetypical business union... until recently! I personally am a UAW member in local 2710, which is somewhat infamous for overthrowing international UAW influence and becoming much more directly democratic, rank and file oriented, and militant. You can read some of that history here. But more significantly, the UAW was recently taken over by reformers in its first-ever direct elections (!!!!) with the promise of a more rank and file and militant approach to labor organizing! Here's an article by Becca Roskill, who served on my local's bargaining committee on the UAW elections.
Also, I wanted to add, there is some really interesting (bad) stuff going on at the intersection of unions and criminalization. Basically, employers are using formerly incarcerated and homeless laborers to circumvent the NYC wage floor. Our sanitation workers are very well unionized and make good money. After big budget cuts over many decades, a demand for cheaper sanitation labor emerged, and it was filled by homeless and formerly incarcerated men who don’t have the option to take better jobs. Unions like Teamsters have been pissed about this for decades but it persists. I wrote an article about it a few years back. There’s similar issues for construction work, where “body shops” employ men for significantly lower wages. Our local Mason Tenders have a campaign specifically integrating formerly incarcerated workers in an effort to push back on this.