Nobody much noticed, but on Aug. 15 Anthony Postiglione went to jail.

According to court testimony, tenants in his 54-room building on West 85th Street, many of them elderly, disabled or on welfare, were assaulted by paid goons in ski masks wielding knives, guns and crowbars. They were locked out of their rooms. Rooms were burglarized and vandalized. Heat and hot water were cut off in mid-winter.

Postiglione, 43, a landlord, got a year in jail and $15,000 in fines after pleading guilty to coercion and conspiracy in forcing low-income residents out of that building and another Manhattan tenement so that expensive housing could be built on the property.

So ended one of the more sordid episodes in a long-running housing war that has engulfed New York neighborhoods from the sedate brownstones of the Upper West Side to seedy streets in Brooklyn.

Postiglione's sentence was the most severe yet for what New Yorkers call the "Wild West" techniques of housing conversion here. But the case was far from unusual. One landlord was convicted of deliberately setting fire to his building to oust remaining tenants. Another tried to drive tenants out by destroying the stairwell. Frequently, landlords need only let a building deteriorate and begin renting to prostitutes and drug addicts; the old tenants soon move out, and the surrounding neighborhood is mobilized to call for renovation.

The buildings are mostly "SROs," New York jargon for single-room occupancy hotels, where a room with shared kitchen and bath rents for about $60 a week. With a severe public housing shortage, SROs are often the only alternative for the poor.

The battles are particularly fierce in newly "gentrified" neighborhoods, such as Brooklyn's Park Slope and Crown Heights or Manhattan's Chelsea and Upper West Side, where upper-middle class professionals pay $1,500 a month to rent one-bedroom apartments and the vacancy rate is less than 2 percent. Most of the SROs have been converted to cooperatives, with apartments selling for $150,000 and up. So efficient are the Wild West techniques that the number of SRO units in New York has plummeted from 127,000 in 1970 to fewer than 18,000 today, an 86 percent drop. During the same period nationwide, about half of the SROs disappeared.

The result is an explosion of homeless people, as former residents of SROs simply take to the streets. Last year 60,000 homeless New Yorkers passed through city agencies. The housing shortage has created a major crisis for the city, which spends $70 million a year to house homeless in emergency shelters and hotels.

The conversion of SROs has been accelerated by New York tax policy, which awards huge rebates to landlords for renovating housing. Before he went to jail, Postiglione received more than $2.1 million in property tax exemptions and abatements for upgrading seven buildings.

A study by the National Institute for Justice in Washington was released last week showing that properties in the tax abatement program were three times more likely to have unexplained fires. One 11-building project suffered 30 fires after a subsidy was applied for.

On the corner of Amsterdam Avenue and 75th Street, a neighborhood where Puerto Rican grocers have given way to Frusen Gladje ice cream stores and unisex hair salons, the 13-story Hotel Lincoln Square houses a mixed group of elderly living on Social Security, welfare recipients and working poor.

In 1981, according to residents, the owners, who had converted several other SROs to luxury housing, stopped renting rooms, decreased services and let the building deteriorate. It was about that time, Pedro Rodriguez remembers, that the former manager, accompanied by two thugs, attacked him with a pipe and told him they would "get rid of him" if he did not move.

Together with other tenants who were allegedly harassed, Rodriguez, 39, a cook, approached the West Side SRO Law Project, a city-funded agency, which helped them organize a tenants group to fight conversion. The Portnoff family, which owns the hotel, did not return a reporter's calls. Today, the Lincoln Square is 40 percent empty, but in the kind of standoff that has become common here, the remaining tenants will not move.

For $64.19 a month Rodriguez rents a single room in which he lives with his wife and three children.

"It's not the greatest," he said. "It's living like sardines in a can. But we don't want to move to Brooklyn, where your kids get mugged when you go to work."

Many of those who pay high rents in gentrified neighborhoods are only too happy to see the SROs disappear, but there is a growing backlash by white liberals who like their mixed neighborhoods. One block association on 87th Street has taken an option and raised nearly $3 million to buy the Capitol Hall SRO in an effort to save it for its mostly minority and elderly tenants.

But Ralph Miller, owner of the Capitol Hall, scoffs at the idea. "There's no room for SROs in a prime area," he said, adding that rent controls prevent landlords from earning enough to maintain the buildings.