When 2,300 employes at The Sun and Evening Sun in Baltimore refused to work last week over a contract dispute, the newspapers' top management wasted no time in matching the union pressure.

Security guards wearing paramilitary jump suits, dark berets and heavy black boots were brought in to watch the picket line and videotape protesters.

By midday of the first day of the strike, supervisors and senior editors had grappled effectively with computers and presses to produce a presentable evening edition of the paper, albeit thinner than usual.

Despite a well-orchestrated strike by 700 members of The Newspaper Guild, the Sunpapers continued publishing. By Tuesday night, a rumor that management was planning the ultimate union-busting tactic -- hiring replacements -- threw fear into members of The Guild and five unions that honored its picket line. Worried about losing their jobs, Sun employes grudgingly accepted a contract that was little improved from an offer made before the walkout.

The six-day walkout in Baltimore is the latest example of how managements are increasingly willing to take on strikes, continue to operate, and even consider hiring replacements if necessary.

This year, in the Washington area alone, there are a number of examples of workers who have lost jobs either by protracted strikes or aggressive lockouts by management. Workers at Scan furniture stores, a retail chain of the Greenbelt Cooperative in Maryland, have been on strike since May 2, but the company has continued operating.

More than 400 seamstresses in Thurmont, Md., have been walking a picket line since April 6, but the Claire Frock Co. factory remains open.

Nearly 100 liquor truck drivers and delivery workers in the District belonging to the Teamsters Union were replaced and have been locked out by management since March 2.

"We were shocked. We were surprised. We didn't expect it," said Ronald Ross, business manager of Teamsters Local 639, whose members were locked out by five liquor distributors. "We didn't even have a chance to take a strike vote. It's a demonstration that management is playing hardball."

Even if the Teamsters had taken a strike vote, it probably would have had little effect, in light of what employe relations consultants and labor experts call a significant increase in management willingness to combat strikes.

One reason for the trend is management's perceived need to cut costs in an era of increased foreign and domestic competition.

But other factors are a nationwide decline in union membership, many workers' willingness to replace strikers and cross picket lines in an era of shrinking industrial jobs, and new technology that not only requires fewer people to put out the same product but also makes it easy for management and strike breakers to operate equipment.

Moreover, the National Labor Relations Board ruled last summer that companies could use temporary replacements for locked-out workers.

"What used to be unthinkable is now standard operating procedure," said Richard Belous of The Conference Board, a major business research group. "The strategy in the '60s and '70s by management was to buy labor peace, look good to the community and pass on the price to the customers.

"Now management can't pass on the cost to customers because of the competition from imports," Belous said. "Now if you fight a strike, you may even be seen as a hero in the community."

The replacement of strikers, a rare phenomenon in post-World War II labor relations, has become relatively commonplace. Major employers such as Continental Airlines, TWA, Greyhound, Phelps Dodge, Iowa Beef Processors, Magic Chef, The Chicago Tribune and many others have done so, in many cases permanently eliminating union members.

The Washington Post in December 1975 hired replacements for the unionized pressmen who had struck the newspaper on Oct. 1 that year.

During the strike, the newspaper continued to publish every day except one as management officials and others operated presses or found alternative places to print the paper.

The willingness of management to take this ultimate step has had a chilling effect on unions, as major strikes declined to a postwar low by 1985.

The causes for the more aggressive management stance are varied, labor experts said. Management became emboldened after President Reagan fired 11,400 members of the Professional Air Traffic Controllers Organization in 1981 for illegally going out on strike.

In ensuing years, decisions by the National Labor Relations Board and advancements in technology have worked to provide added incentives for management in industries including steel, air travel and telecommunications to work through strikes.

"Unions have to be much more careful before they call a strike," said Douglas Fraser, former president of the United Auto Workers and currently professor of labor at Wayne State University. "A strike once was an economic contest between management and the employe. But now companies are going in to break the union. They make no movement at the table. They ask for concessions. They go into a strike not to soften the union's position but to destroy them."

Spokesmen for corporate managements said their aggressive posture is driven not by antiunionism but by competitive conditions. The impact of deregulation, such as in the airline industry, and the emphasis on cutting costs in almost every industry facing foreign competition have created tougher bargaining and a willingness to operate through strikes.

"There's enormous competitive pressures that are pushing management to take a hard-line approach," said William J. Curtin, a prominent Washington management lawyer. "As I see it, it's not an effort to break the union. It's an effort to cut costs. And one of the few things you can attempt to control is your labor costs."

Richard Basoco, general manager of the Sunpapers, said last week that management would have hired replacements for some of its commercial workers if the strike had continued.

"There was no specific plan to hire workers," he said. "But obviously the paper was getting bigger day by day and we {would} have had to restaff if the strike had continued . . . . I don't regard that as a threatening issue. It was just a business decision."

Statistics from the Bureau of National Affairs publishing company and The Conference Board demonstrate the trends in strikes and lockouts.

Lockouts, a step by management to close its doors to union workers who have threatened a strike, jumped 44 percent, from 23 in 1985 to 41 in 1986. But the number of strikes dipped significantly in the same period, from 968 to 773, BNA statistics show.

Organized labor is trying to address these conditions by finding ways to avoid striking, but taking action in other ways. The AFL-CIO recently produced a manual for its members called "The Inside Game: Winning With Workplace Strategies," which emphasizes union organizing, work slowdowns and campaigns to influence the corporate image in the community.

An example of the success of such tactics is the experience of employes at McDonnell Douglas Corp. who have been working without a contract since last fall.

For months, employes in the International Association of Machinists & Aerospace Workers have been finishing only the work required by contract, and completing those tasks only according to specific language.

According to union officials, such action has invigorated union members and caused serious and costly slowdowns for the company.

The United Auto Workers, which pioneered such alternative strategies, calls it "running the plant backwards."

"We're looking for alternatives," said Joseph Uehlein, director of special projects for the AFL-CIO. "We're developing strategies that, if effective, could be close to guerrilla warfare day to day on the shop floor."

In Baltimore, union organizers said last week that the Guild strike helped unite sometimes disparate union groups throughout the Sun operation.

As a result of the Guild contract, pressmen who recently agreed to a contract with poorer health benefits were able to renegotiate for themselves a package similar to the Guild's.

If the walkout did little to improve the final contract accepted by the Guild, many say, it somehow has created a sense of enthusiasm for the union and among employes from both newspapers that is surprising to some people.

"I think we learned a lesson here," said Michael Wentzel, a reporter with The Evening Sun. "I don't think this frightened us as much as it taught us some tactics."