It caught almost everyone in Alexandria City Hall by total surprise.

Vice Mayor James Moran got the word in a phone call one afternoon earlier this month but didn't believe it: City Manager Douglas Harman had appointed Police Chief Charles Strobel to a new position, public safety director, giving the top policeman control over the 220-member Fire Department.

"I can tell you that can't be true," Moran says he assured the caller, "because the manager would never do anything that major without first checking with the council."

Moran was wrong. As City Council members learned from a memo that Harman sent to their homes by messenger that evening, Strobel would remain in his $62,000 job as police chief but also become boss to a man who had been his equal for six years, Fire Chief Charles Rule.

Strobel's promotion ignited a City Hall flap that left some council members feeling Harman should consult them more closely, Harman promising the move will help cut fire and police costs, and Chief Rule hinting he might take his services elsewhere.

At the bottom of the issue lies a long-term attempt by Harman to insulate his office from the day-to-day headaches of city administration and to better coordinate police and fire functions and attack their costs. It is a quandary facing his counterparts in other Northern Virginia jurisdictions.

"When I first came here in 1976, there were 27 persons reporting directly to the city manager," Harman says. He says the figure is now down to about 15 and will drop further soon when he combines some building, health and fire inspection services.

Despite the surprise, Strobel's new job seems to have caused no significant damage to relations between council and manager. Moran says the council would have approved had it only had the chance.

Turf battles between fire and police departments have traditionally been a standard feature of municipal government around the country. Harman says his intent was to move decisively on an issue that was certain to be controversial: "If you had set it out for great public debate, it would have lent itself to inappropriate administrative politicking."

The affair has prompted endless phone calls and speculation in City Hall about how the two principals, Strobel and Rule, were taking to their new roles.

For Strobel, a 45-year-old Alexandria native with the measured words and rugged good looks of a frontier marshal, the new hat is the latest of an almost routine progression of promotions since he began his police career as a patrolman on the city's streets 25 years ago.

He responded to the news of his new job in character. "I'm not interested in empire-building," he told a reporter last week. "I'm only interested in being a public servant and doing the duties that have been assigned to me."

Strobel will eventually have a permanent symbol of his new standing--a $20 million public safety center that is to be built off the Capital Beltway to bring the Alexandria City Jail, police headquarters and other offices under one roof.

Rule, mustachioed and affable at 47, was hired by Harman to his $59,000-a-year job in 1976 from a small town in Ohio and has built a reputation as an unconventional manager who is not hesitant to speak his mind.

In 1978, he attracted national media attention with a decision to outlaw smoking by firefighters--both on and off the job--under penalty of dismissal. (No one has ever been fired, but Rule thinks his regulation has been effective.) More recently, he tangled with local water authorities over why water pressure in some city hydrants was substandard.

Rule reacted in form to the news of his effective demotion, which he says he got only a day before the council members. "I think the way it was handled was shabby . . . it makes for very poor employe relations," he told a reporter. If things didn't work out, he said, he might look for a job elsewhere.

Since the change became effective, Rule and Strobel have held several meetings (alternating between their two offices) to discuss "philosophy" of emergency services, Rule says. Rule says the meetings have been cordial, but he does not know what will grow from the change. "I have not been privy to what the grandiose plan is," he says.

"I see the objective as better coordination between police and fire . . . in a more cost-efficient manner," says Strobel. "The cost of government today is foremost in most people's minds."

Harman has made it clear that one thing he wants to examine soon is the practice of sending a fully equipped fire truck as back-up on ambulance calls involving serious illness or injury. Sending a police cruiser along would be cheaper, it is argued. Rule points out that his firefighters have better medical training than police officers do.

In a memo to council members, Harman also laid out long-range plans to look at contracting for emergency services from neighboring jurisdictions and consolidating some police and fire functions to reduce overhead.