When Prince George's County Executive Lawrence J. Hogan unveiled his strategy for low- and moderate-income housing a few weeks ago, he declared war on slumlords. His secret weapon was to be the county's power to enforce housing codes.

Figures released recently by the Department of Licenses and Permits indicate, however, that the war actually began more than a year ago.

The results are a mixed blessing for dwellers of Prince George's rental units. These results include: more compliance by landlords with county housing codes, higher rents for tenants and a tightening of the low- and moderate-income housing market in the county.

During 1979, the Department of Licenses and Permits revoked, suspended or denied 80 apartment licenses in the county, as compared with nine in 1978, and 10 in 1977.

The crackdown is aimed at eliminating deplorable living conditions such as those cited by county inspectors at the Belle Haven East Apartments in Landover. Among the nearly 255 violations found last November were "unsanitary hallways, rodent and rat infestation, numerous broken light fixtures, and accumulation of rubbish in and around the building," according to housing inspectors' records.

As a result of the 80 license actions, 12,385 apartment units were temporarily taken out of the housing market, approximately 12 percent of the county's 100,000 units. Apartment owners who do not have licenses cannot rent vacant units until housing code violations are corrected.

The comparable number of units temporarily out of the market in the past were 1,685 in 1978, and 2,090 in 1977. Although the units were usually back on the market in a few months, the end effect was to decrease the number of apartments available, thereby tightening the housing market.

Joseph Healey, deputy director of the licenses and permits department, said owners' unwillingness to commit large sums of money, coupled with poor management and bad tenants, have led to the large number of problem projects in the county.

"With enough neglect, it's easy to reach that point of no return," said Healey.

In some cases, inspectors have declared rundown buildings unsafe for human habitation.

For example, several apartments in the Suitland Manor development were boarded up after deterioration set in, eventually leading the licenses and permits department to cite the buildings as fire hazards.

In the case of one building, the owner's license was revoked in June 1978 and he has still not been able to bring the building up to code.

In another aspect of the get-tough policy on slumlords, the Department of Licenses and Permits has threatened owners whose licenses are taken away with the closure of projects that have vacancy rates of 50 percent or higher.

Until now, only one such project has been closed -- the 625-unit Pumpkin Hill Apartments in south Laurel. Owners of that complex gave the project back to the Department of Housing and Urban Development after being cited for hundreds of housing code violations. Approximately 70 families had to find new homes after that action was taken last spring. Many tenants had left before the order came down.

Even so, the closure angered many black community leaders who felt that the new administration in Upper Marlboro had declared war not on county slumlords but on the tenants whom the stricter enforcement of housing codes was aimed at protecting.

Several prominent black and white county political leaders considered contesting in court the eviction of the tenants, all of whom fell into the low- to middle-income bracket. However, HUD and county officials recently reached an agreement under which approximately 105 units will be destroyed and the remainder will be repaired to bring them up to code.

Once the project reopens, about 20 percent of the units will be made available to low-income tenants who have federal rent-subsidy certificates.

The power to declare an entire development unsafe for human habitation, and to evict all tenants has been kept in reserve as a weapon of last resort. Most landlords whose buildings have been cited for code violations have made necessary repairs within several months.

"In the past, I think there was a tendency to give private developers more time to comply with housing codes before taking their licenses," said Healey, who has been in charge of apartment inspections for most of the last seven years.

"Now we're willing to hit the slumlords in the pockets and not give them any extensions. There's no question it really hurts them when they can't rent vacant apartments. They realize then that they are either going to have to keep their properties up or we're going to shut them down."

Thus far, the compliance rate among landlords cited for code violations has been high. Nearly 83 percent of owners whose licenses were revoked last year have brought their properties up to code and have their licenses back.

The get-tough policy has even begun to have an impact on projects constantly plagued by housing code violations over the years.

Take, for example, the case of the Belle Haven East Apartments, which have been a regular since 1972 on the list of buildings with numerous housing code violations, according to a county official. Inspectors found nearly 255 violations in the complex last November. Tenants complain about unsanitary conditions, the slowness with which management makes repairs and unlighted hallways and parking lots.

"If you want the hallways around here cleaned, you have to do it yourself, "said Donna Parker, who has lived at Belle Haven for two years. "And down in the wash (laundry) room, I've seen rats as big as rabbits."

Security has also been a problem.

"I heard about a couple of cases where people got mugged or raped because of all of the broken lights in the hallways and outside," said Debra Isom, another two-year resident of Belle Haven.

Seat Pleasant District police commander Wayne R. Croyle said, "The records show that there were around 15 muggings in the area but we can't really be sure that all of the Belle Haven development was covered (in the records). One crime is one too many, but 15 muggings isn't very far out of line with other developments in the area."

Because little improvement had been made by mid-January, the licenses and permits department refused to give a new license to the Chase Manhattan Bank of New York, which owns the Belle Haven East Apartments.

About two weeks ago, Chase hired the Wingate Management Company to operate the project, making Wingate the third management firm to have control of the project in the last two years.

Already, the company is making an attempt to turn the 401-unit complex around -- repairing lights, putting outside doors on the apartment buildings and renovating the many boarded-up apartments.

While the new management firm tries to rescue Belle Haven, others question whether it can be done.

"With stricter enforcement of the housing codes, a lot of companies are going to have to think long and hard about how much money they want to spend on a place like Belle Haven," said I.R. King, president of Research Realty Management Inc., the firm which ran the project until mid-January.

"Projects like this aren't making any money right now, and it becomes a question of how much subsidizing an owner is willing to do before the project is turned around," he added.

Except for the Pumpkin Hill controversy last spring, the new policy of stringent enforcement has been supported by most community leaders and landlords.

"We've always favored stringent enforecement of the housing codes," said Carolyn Lewis, legislative liaison for the Apartment and Office Building Association, which has as its members landlords from Prince George's and other jurisdictions in the metropolitan area.

County Council member Deborah Marshall, one of the leaders who threatened to file a suit against the county for evicting the tenants of Pumpkin Hill, said the new policy creastes "a catch-22 kind of a situation. No one wants to see people living in sub-standard housing so you have to favor strict enforcement of the codes, but on the other hand, no one wants to see people thrown out in a blizzard.

"The key to this whole new strategy is what will the executive do to help the families that may in the future be displaced by apartment failures and what can we do to make sure tenants don't bear all of the financial burdens of the repairs made."

Healey says that, at present, tenants asked to vacate condemned buildings can call the county executive's office of citizens affairs for help in finding housing.