This is a union at war.

You can feel it as soon as you walk into the International Longshoremen's and Warehousemen's Union Hall near the Los Angeles waterfront.There is suspicion. Questions are asked and identification is checked. Once everything is settled, relations are less stiff. Still, words are guarded.

Some of the rank-and-file members repeat rumors that undercover police have tried to infiltrate their ranks. Why? "To get information - find out what we're doing," declares one longshore worker.

Others nod. It's a group of about 12 longshore workers, most of whom were laid off the day before. They used to work at the Intermodal Container Transfer Facility operated by Southern Pacific Transportation Co. SP, however, decided to take the operation in-house, turning over the jobs to rail workers and dismissing some 335 longshore workers who manned the facility since its opening.

Now those longshore workers take turns passing out leaflets and demonstrating at their former place of employment. In between shifts, they come to the Local 13 union hall.

Talking to them, it becomes apparent that they feel they were not only robbed of their jobs, but their dignity.

"They even sent us somewhere else to be paid," laments one union member.

The day they were ordered off the facility, Feb. 11, they were told to go pick up their final paychecks at a business office located away from the container yard. Once they arrived at the business office they were met in the parking lot and paid off in cashier's checks. The manager of a restaurant that shares the parking lot came out at one point and complained about the crowd.

As they see it, their only sin was in choosing a strong 50,000-member union that negotiated a tough contract with the railroad. They'll tell you the railroad is cutting them out to void the contract.

"We're caught in the middle," said David Arian, ILWU president, in a brief interview at the Long Beach airport. SP, he said, is trying to carve up and sell its property and operations to keep going. The ILWU's presence at the Los Angeles ICTF interfered with that program, he said.

Mr. Arian and other longshore officials are gathering in the Los Angeles- Long Beach area this weekend to hold a rally. The demonstration is supposed to culminate in a coastwide longshore strike on Monday.

Legal maneuvering around the strike is already under way. But the strategy the longshore workers are trying to employ is clear. By pressuring the maritime community, they hope to isolate the SP intermodal yard.

"This yard cannot function without the good will of the maritime industry and the maritime worker," Mr. Arian recently said on a local radio show.

That statement is recorded on a videotape that plays on a monitor at the union hall. The tape shows scenes from the intermodal yard or, as it is occasionally subtitled, "the scab training facility."

Meanwhile, union members continue to quietly picket outside the SP intermodal container facility. They vow to maintain their vigil 24 hours a day.