RICHMOND, Va. — Five years ago, Amazon was compelled to post a “notice to employees” on the break-room walls of a warehouse in east-central Virginia.

The notice was printed simply, in just two colors, and crammed with words. But for any worker who bothered to look closely, it was a remarkable declaration. Amazon listed 22 forms of behavior it said it would disavow, each beginning in capital letters: “WE WILL NOT.”

“We will not threaten you with the loss of your job” if you are a union supporter, Amazon wrote, according to a photo of the notice reviewed by The New York Times. “We will not interrogate you” about the union or “engage in surveillance of you” while you participate in union activities. “We will not threaten you with unspecified reprisals” because you are a union supporter. We will not threaten to “get” union supporters.

Amazon posted the list after the International Association of Machinists and Aerospace Workers accused it of doing those very things during a two-year-long push to unionize 30 facilities technicians at the warehouse in Chester, just south of Richmond. While Amazon did not admit to violations of labor laws, the company promised in a settlement with federal regulators to tell workers that it would rigorously obey the rules in the future.

The employee notice and failed union effort, which have not previously been reported, are suddenly relevant as Amazon confronts increasing labor unrest in the United States. Over two decades, as the internet retailer mushroomed from a virtual bookstore into a $1.5 trillion behemoth, it forcefully — and successfully — resisted employee efforts to organize. Some workers in recent years agitated for change in Staten Island, Chicago, Sacramento and Minnesota, but the impact was negligible.

The arrival of the coronavirus last year changed that. It turned Amazon into an essential resource for millions stuck at home and redefined the company’s relationship with its warehouse workers. Like many service industry employees, they were vulnerable to the virus. As society locked down, they were also less able to simply move on if they had issues with the job.

Now Amazon faces a union vote at a warehouse in Bessemer, Ala. — the largest and most viable U.S. labor challenge in its history. Nearly 6,000 workers have until March 29 to decide whether to join the Retail, Wholesale and Department Store Union. A labor victory could energize workers in other U.S. communities, where Amazon has more than 800 warehouses employing more than 500,000 people.

“This is happening in the toughest state, with the toughest company, at the toughest moment,” said Janice Fine, a professor of labor studies at Rutgers University. “If the union can prevail given those three facts, it will send a message that Amazon is organizable everywhere.”

Even if the union does not prevail, “the history of unions is always about failing forward,” she said. “Workers trying, workers losing, workers trying again.”

The effort in Chester, which The Times reconstructed with documents from regulators and the machinists’ union, as well as interviews with former facilities technicians at the warehouse and union officials, offers one of the fullest pictures of what encourages Amazon workers to open the door to a union — and what techniques the company uses to slam the door and nail it shut.

The employee notice was a hollow victory for workers. The National Labor Relations Board, the federal agency that negotiated the settlement with Amazon, has no power to impose monetary penalties. Its enforcement remedies are few and weak, which means its ability to restrain anti-union employers from breaking the law is limited. The settlement was not publicized, so there were not even any public relations benefits.

Amazon was the real winner. There have been no further attempts at a union in Chester.

The tactics that Amazon used in Chester are surfacing elsewhere. The retail workers union said Amazon was trying to surveil employees in Bessemer and even changed a traffic signal to prevent organizers from approaching warehouse workers as they left the site. Last month, the New York attorney general said in a lawsuit that Amazon had retaliated against employees who tried to protest its pandemic safety measures as inadequate.

Amazon declined to say whether it had complied with labor laws during the union drive in Chester in 2014 and 2015. In a statement, it said it was “compliant with the National Labor Relations Act in 2016” when it issued the employee notice, and “we continue to be compliant today.” It added in a different statement that it didn’t believe the union push in Alabama “represents the majority of our employees’ views.”

The labor board declined to comment.

The Chester settlement notice mentions one worker by name: Bill Hough Jr., a machinist who led the union drive. The notice said Amazon had issued a warning to Mr. Hough that he was on the verge of being fired. Amazon said it would rescind the warning.

Six months later, in August 2016, Amazon fired him anyway.

Mr. Hough (pronounced Huff) was in a hospital having knee surgery when Amazon called and said he had used up his medical leave. Since he couldn’t do his job, he said he was told, this was the end of the line.

“There was no mercy, even after what they had done to me,” Mr. Hough, now 56, said. “That’s Amazon. If you can’t give 110 percent, you’re done.”

Amazon declined to comment on Mr. Hough.

No Constraints

Amazon was founded on notions of speed, efficiency and hard work — lots of hard work. Placing his first help wanted ad in 1994, Jeff Bezos, Amazon’s founder, said he wanted engineers who could do their job “in about one-third the time that most competent people think possible.”

Amazon managers openly warned recruits that if they liked things comfortable, this would be a difficult, perhaps impossible, job. For customer service representatives, it was difficult to keep up, according to media accounts and labor organizers. Overtime was mandatory. Supervisors sent emails with subject headings like “YOU CAN SLEEP WHEN YOU’RE DEAD.”

In 1999, the reps, who numbered about 400, were targeted by a grass-roots group affiliated with the Communications Workers of America. Amazon mounted an all-out defense.

If workers became anything less than docile, managers were told, it was a sign there could be union activity. Tipoffs included “hushed conversations” and “small group huddles breaking up in silence on the approach of the supervisor,” as well as increased complaints, growing aggressiveness and dawdling in the bathroom.

Amazon was in sync with the larger culture. Unions were considered relics of the industrial past. Disruption was a virtue.

“Twenty years ago, if you asked whether the government or workers should be able to put any constraints on companies, the answer always was ‘No constraints,’” said Marcus Courtney, a labor organizer on the 1999 Amazon campaign. “If companies wanted to push people 365 days a year, 24 hours a day, hats off to them.”

When the dot-com bubble burst in 2000, Amazon lost some of its glow. For a time, its very existence was in question.

This caused problems for the activists as well. The company reorganized and closed the customer service center, though Amazon said there was no connection with the union drive. The United Food and Commercial Workers Union and the Prewitt Organizing Fund, an independent group, made no inroads organizing Amazon’s 5,000 warehouse workers.

A decade later, in 2011, came a low point in Amazon’s labor history. The Morning Call newspaper in Allentown, Pa., revealed that Amazon was hiring paramedics and ambulances during summer heat waves at a local warehouse. Workers who collapsed were removed with stretchers and wheelchairs and taken to hospitals.

Amazon installed air conditioning but otherwise was undaunted. After the Great Recession in 2008, there was no lack of demand for its jobs — and no united protest about working conditions. In Europe, where unions are stronger, there were sporadic strikes. In the United States, isolated warehouse walkouts drew no more than a handful of workers.

The Machinist

Mr. Hough worked as an industrial machinist at a Reynolds aluminum mill in Richmond for 24 years. He once saw a worker lose four fingers when a steel roller fell unexpectedly. Incidents like that made a deep impression on him: Never approach equipment casually.

Reynolds closed the plant in the Great Recession, when Mr. Hough was in his mid-40s. Being in the machinists guild cushioned the blow, but he needed another job. After a long spell of unemployment, he joined Amazon in 2013.

The Chester warehouse, the size of several aircraft carriers, had opened a year earlier, part of Amazon’s multibillion-dollar push to put fulfillment centers everywhere. Mr. Hough worked on the conveyor belts bringing in the goods.

At first, he received generally good marks. “He has a great attitude and does not participate in negative comments or situations,” Amazon said in a March 2014 performance review. “He gets along with all the other technicians.”

But Mr. Hough said he had felt pressured to cut corners to keep the belts running. Amazon prided itself on getting purchases to customers quickly, and when conveyor belts were down that mission was in jeopardy. He once protested restarting a belt while he was still working on it.

“Quit your bitching,” Mr. Hough said his manager, Bryon Frye, had told him, twice.

“That sent me down the wrong road,” Mr. Hough said.

Mr. Frye, who declined to comment, no longer works for Amazon. On Twitter last month, he responded to a news story that said Amazon was hiring former F.B.I. agents to deal with worker activism, counterfeiting and antitrust issues.

“This doesn’t shock me,” he wrote. “They do some wild things.”

The Union Drive

In 2014, Mr. Hough and five other technicians approached the International Association of Machinists and Aerospace Workers. A unionization effort was already taking place with the technicians at an Amazon warehouse in Middletown, Del. If either succeeded, it would be the first for Amazon.

The elections for a union would be conducted by the National Labor Relations Board. The first step was to measure interest. At least 18 of the 30 technicians in Chester returned cards indicating their willingness to be represented by the union.

“It was not too difficult to sign people up,” said Russell Wade, a union organizer there. “But once the word leaked out to Amazon, they put the afterburners on, as employers do. Then the workers started losing interest. Amazon spent oodles of money to scare the hell out of employees.”

The board scheduled an election for March 4, 2015. A simple majority of votes cast would establish union representation.

Amazon brought in an Employee Resource Center team — basically, its human resources department — to reverse any momentum. A former technician at the warehouse, who declined to be named for fear of retaliation, said the reps on the team followed workers around, pretending to be friendly but only seeking to know their position on the union drive.

If safety was the biggest issue for the technicians, there were also concerns over pay equity — machinists said they were paid different amounts for doing the same job — and about their lack of control over their fate. Part of Mr. Hough’s pitch was that a union would make management less arbitrary.

“One guy, all I remember is his name was Bob,” he said. “They paged Bob to the control room, and the next thing I saw was Bob coming down the steps. He had taken off his work vest. I said, ‘Bob, where are you going?’ He said, ‘They terminated me.’ I didn’t ask why. That’s the way it was.”

Several technicians said they recalled being told at a meeting, “You vote for a union, every one of you will be looking for a job tomorrow.” At another, the most outspoken union supporters were described as “a cancer and a disease to Amazon and the facility,” according to Mr. Hough and a union memo. (In a filing to the labor board, Amazon said it had investigated the incident and “concluded that it could not be substantiated.”)

Mr. Hough, a cancer survivor, said the reference had offended him. He declined to attend another meeting run by that manager. He said he had known in any case what she was going to say: that the union was canceling the election because it thought it would lose. Amazon had triumphed.

On March 30, 2015, Mr. Hough received a written warning from Mr. Frye, his manager.

“Your behavior has been called out by peers/leaders as having a negative impact,” it said. Included under “insubordination” was a refusal to attend the Amazon victory announcement. Another incident, Amazon said, could result in termination.

The machinists union filed a complaint with the labor board in July 2015 alleging unfair labor practices by Amazon, including surveilling, threatening and “informing employees that it would be futile to vote for union representation.” Mr. Hough spent eight hours that summer giving his testimony. While labor activists and unions generally consider the board to be heavily tilted in favor of employers, union officials said a formal protest would at least show Chester technicians that someone was fighting for them.

In early 2016, Amazon settled with the board. The main thrust of the two-page settlement was that Amazon would post an employee notice promising good behavior while admitting nothing.

Wilma Liebman, a member of the labor board from 1997 to 2011, examined the employee notice at the request of The Times. “What is unusual to my eye is how extensive Amazon’s pledges were, and how specific,” she said. “While the company did not have to admit guilt, this list offers a picture of what likely was going on.”

Amazon was required to post the notice “in all places where notices to employees are customarily posted” in Chester for 60 days, the labor board said.

From the machinists union’s point of view, it wasn’t much of a punishment.

“This posting was basically a slap on the wrist for the violations that Amazon committed, which included lies, coercion, threats and intimidation,” said Vinny Addeo, the union’s director of organizing.

Another reason for filing an unfair labor practices claim was that the union hoped to restart its efforts with a potentially chastened company. But most of the employees who supported the Chester drive quit.

“They were intimidated,” Mr. Wade, the union organizer, said.

Mr. Hough was beset by ill health during his years at Amazon. Radiation treatment for his cancer prompted several strokes. His wife, Susan, had health problems, too. Mr. Hough said he wondered how much the unionization struggle contributed to their problems. He added that he didn’t know whom to trust.

After leaving Amazon, Mr. Hough began driving trucks, at first long haul and later a dump truck. It paid less, but he said he was at peace.

Maximum Green Times

When Amazon vanquished the 2014 union drive in Delaware, the retailer said it was a victory for “open lines of direct communication between managers and associates.”

One place Amazon developed that direct communication was in its warehouse bathrooms under what it called its “inSTALLments” program. The inSTALLments were informational sheets that offered, for instance, factoids about Mr. Bezos, the timing of meetings and random warnings, such as this one about unpaid time off: “If you go negative, your employment status will be reviewed for termination.”

As the union drive heated up in Bessemer, the direct communication naturally was about that. “Where will your dues go?” Amazon asked in one stall posting, which circulated on social media. Another proclaimed: “Unions can’t. We can.”

Amazon also set up a website to tell workers that they would have to skip dinner and school supplies to pay their union dues.

In December, a pro-union group discovered, Amazon asked county officials to increase “maximum green times” on the warehouse stoplight to clear the parking lot faster. This made it difficult for union canvassers to approach potential voters as they left work. Amazon declined to comment.

Last month, President Biden weighed in.

“There should be no intimidation, no coercion, no threats, no anti-union propaganda,” he said in a video that never mentioned Amazon but referred to “workers in Alabama” deciding whether to organize a union. “You know, every worker should have a free and fair choice to join a union. The law guarantees that choice.”

Owning 25 Hats

Mr. Hough, in an interview before the pandemic, said part of him wanted to forget what had happened at Amazon. Why dwell on defeat? He threw away all the papers from the union drive. He never saw the employee notice because he was recovering from a stroke.

But he has not forgiven the retailer.

“You’re only going to step on me one time,” he said, sitting in his home in the outskirts of Richmond.

Amazon’s customers just don’t know how miserable a job there can be, he suggested.

“I guarantee you, if their child had to work there, they’d think twice before purchasing things,” he said.

Ms. Hough, sitting next to him, had a bleaker view.

“The customers don’t care about unions. They don’t care about the workers. They just want their packages,” she said.

As if on cue, their son, Brody, came in. He was 20, an appliance technician. His mother told him there was a package for him on his bed. It was from Amazon, a fishing hat. It cost $25, Brody said, half the price on the manufacturer’s website.

“I order from Amazon anything I can find that is cheaper,” Brody said. That adds up to a lot of hats, about 25. “I’ve never worked for Amazon. I can’t hate them,” he said.

Ms. Hough looked at her husband. “If your own son doesn’t care,” she asked, not unkindly, “how are you going to get the American public to care?”

The pandemic helped change that, bringing safety issues at Amazon to the forefront. In a Feb. 16 suit against Amazon, the New York attorney general, Letitia James, said the company continued last year to track and discipline employees based on their productivity rates. That meant workers had limited time to protect themselves from the virus. The suit said Amazon retaliated against those who complained, sending a “chilling message” to all its workers. Amazon has denied the allegations.

Last week, regional Canadian authorities also ordered thousands of workers at an Amazon warehouse near Toronto to quarantine themselves, effectively closing the facility. Some 240 workers recently tested positive for the virus there, a government spokeswoman said, even as the rate of infection in the area fell. Amazon said it was appealing the decision.

Alabama is now the big test. Mr. Hough worries the union supporters will be crushed.

“They will fall to threats or think, ‘I won’t have a job, Amazon will replace me,’” he said by phone this month. “When a company can do things to you in secret, it’s real hard to withstand.”

Still, he added, “I’m hoping for the best. More power to them.”