When 36,000 Verizon employees walked off the job Wednesday, the action represented one of the biggest work stoppages in the country since the last strike at the telecommunications giant in 2011. The workers’ aggressive stance reflects the turmoil in an industry undergoing rapid technological change while its veteran workforce fights to protect its jobs.

The striking workers, including about 5,000 in Massachusetts, are repairmen, installers, customer service representatives, and other East Coast service workers for Verizon’s wireline business, which provides land-line phone and FiOS service. The action came a day after Verizon announced a $300 million investment to bring high-speed fiber-optic FiOS Internet and TV service to Boston.

The workers, represented by the Communications Workers of America and the International Brotherhood of Electrical Workers, have been without a contract for nearly eight months. The unions say Verizon wants to freeze pensions, make layoffs easier, and rely more on contract workers. The telecom company has said there are health care issues that need to be addressed for retirees and current workers because medical costs have grown. The company also says it wants greater flexibility in managing its workers.

“Unfortunately, union leaders have their own agenda rooted in the past and are ignoring today’s digital realities,’’ Marc Reed, Verizon’s chief administrative officer, said in a statement. “Calling a strike benefits no one.’’

Myles Calvey, business manager for IBEW Local 2222 in Dorchester, said the technicians on strike are highly involved in new technologies, including maintaining fiber-optic networks and upgrading streaming services. Bringing FiOS to Boston will further increase demand for their services.

“The good news is we’re going to have ­FiOS in Boston,’’ Calvey said. “The bad news is we’re going to be on strike.’’

As the rate of union membership nationwide has declined, from 20 percent of the workforce in 1983 to 11 percent today, strikes have become increasingly rare. Last year there were 12 major work stoppages, involving 47,000 workers, according to the Bureau of Labor Statistics; in 1970, there were 381, representing 2.5 million workers.

Verizon Communications Inc., which has a total workforce of more than 177,000 employees, was formed in 2000 following the mergers of several cable and telephone companies. Three of the five contract negotiations since have led to strikes — all of them among the biggest strikes in recent years. Gary Chaison, a professor of industrial relations at Clark University, said the frequency of strikes is a result of “workers who are militant and are employed in an industry that is undergoing some real major changes.’’

“In past negotiations, the workers at Verizon were trying to see what they could gain from Verizon; now they’re trying to see what they can protect,’’ Chaison said. “It epitomizes the predicament of the labor movement. Negotiations are primarily defensive actions to protect jobs.’’

Public support of unions has declined in recent years, although Democratic presidential candidate Bernie Sanders was quick to join workers on the picket line in Brooklyn.

“Both sides are I think gambling with what the public reaction is going to be,’’ said Russ Davis, executive director of the workers’ advocacy group Massachusetts Jobs With Justice. “Everything that’s being talked about in the presidential race is relevant to this fight. For us, ­Verizon is the poster child for what’s wrong with the American economy. It’s a highly profitable company. There’s no reason for them to demand concessions.’’

Verizon, which generated a $17.9 billion profit last year, is the country’s second largest telecom company, after AT&T.

Each Verizon contract has chipped away at long-established benefits, said Keith Bonasoro, a 19-year veteran who was among the approximately 100 Verizon workers picketing in Bowdoin Square Wednesday. Job guarantees, pension plans, and free health care benefits have all gone away, he said.

Without the union, “these jobs would be off-shored in a heartbeat,’’ said Bonasoro, 44, of Weymouth. “Nobody chooses this. What we’re doing here is we’re protecting American jobs. They want to constantly off-shore, outsource good middle-class jobs that support our community. There’s growing public sentiment against corporate greed.’’

Bryan Phillips, a third generation Verizon worker from Pembroke, said he fears for his job every time a contract is up.

“I didn’t want to go on strike, none of us did, but at the same time, enough’s enough. Not just for Verizon but everywhere,’’ said Phillips, 38, who has been a technician for 18 years. “You don’t see anyone [in other companies] go on strike, because they’re all afraid. They’re afraid they’re going to lose their jobs. But if we don’t fight for these jobs, these jobs won’t be here.’’

In addition to sending call center jobs overseas, and outsourcing work here to low-wage contractors, Verizon has been pushing to transfer workers away from their families for months at a time, according to the unions. Tom Juravich, a labor studies professor at the University of Massachusets Amherst who wrote about ­Verizon in his 2009 book “At the Altar of the Bottom Line,’’ called Verizon’s work practices “positively 19th century.’’

All 160 wire-line Verizon locations around the state are on strike, said Calvey, of IBEW Local 2022, and customers who need installation or maintenance should be prepared for disruptions. Verizon said that the company has trained thousands of nonunion workers to fill in for striking workers, and that employees from other departments will be sent to replace striking workers.

‘‘Let’s make it clear, we are ready for a strike,’’ said Bob Mudge, president of Verizon’s wireline network operations.

The company did not respond to questions about whether customers experienced service disruptions on Wednesday.

The majority of Verizon Wireless workers are not part of the strike, although one organized location in Everett is participating in the work stoppage, and the union is picketing other wireless locations.

Scott Garland, a central office technician who works on network equipment, was picketing with other technicians Wednesday morning in Milton. He said Verizon’s proposals would hurt longtime workers and customers, as the company turns its attention to newer technologies.

“Corporate heads have decided to let much of the network wither away,’’ said Garland, 41, who has been with the company for 17 years. “They’re really trying to take away everything those who built the network, and from the consumers themselves.’’

Material from the Associated Press was used in this report. Katie Johnston can be reached at katie.johnston@globe.com and on Twitter @ktkjohnston.