LIMA, PERU -- The first thing Alberto Fujimori did after taking office as president was to fire the commanders of the navy and air force. Then he launched a bitter attack on the slow-moving, corruption-ridden judiciary, calling some judges "jackals." Now he has squared off against the Roman Catholic Church, blasting its "medieval and recalcitrant" attitudes toward birth control.

He has snubbed the evangelical Christian groups whose support was crucial in his election victory. He has told the United States to keep its millions for help in the drug fight until it designs a program he likes better. He has imposed a stern economic program known as "Fujishock" that is based on policies he denounced during the campaign.

All this hardly sounds like a recipe for success for a neophyte president who does not even have an organized political party to back him up, let alone a legislative majority. Yet somehow, Latin America's most improbable head of state is pulling it off.

Earlier this year, Fujimori, 52, came out of nowhere to beat novelist Mario Vargas Llosa for the presidency. Now, three months after being sworn in, he continues to surprise, particularly with his political skills.

"He's very skillful," said political scientist Fernando Rospigliosi of the Institute of Peruvian Studies. "But he's playing a dangerous game."

A recent poll by the survey firm DATUM showed the new government's popularity hovering around 60 percent -- a decline from when Fujimori first took office but still respectably high for a government that has raised gasoline prices 30-fold, allowed the prices of basic foodstuffs to double or triple and taken a host of other tough anti-inflation measures.

Meanwhile, a survey by another firm shows Fujimori winning the approval of two-thirds of Peru's businessmen -- most of whom had worked to keep him from being elected.

"I hear business people who were extremely contemptuous of Fujimori saying, 'Thank heavens Vargas Llosa didn't get elected,' " said a diplomatic source. "Fujimori has imposed what they see as the right policies but without the social costs that there would have been if Vargas Llosa and the upper class had done the same things."

Fujimori's style of governing has been to play parties, factions and individuals against one another while retaining control for himself. Some observers predicted that Fujimori, because of his inexperience, would be overshadowed by his cabinet. But while he has given some measure of autonomy to Economy Minister Juan Carlos Hurtado Miller, who has been running the adjustment program, Fujimori personally directs most other government policies.

As a result, no announcement, statement or trial balloon that comes out of the presidential palace carries weight unless it comes from Fujimori. He has been combative and at times stubborn. "He'll tread on anybody's toes to get the people and the things he wants in place," said a diplomat.

Among those most disappointed by Fujimori's style are the evangelical Christians who form the most tightly knit bloc of Fujimori's Change 90 movement. These Protestants had hoped for a major voice in the new administration and for government policies that would begin to give their churches a status closer to that of the Roman Catholic Church, to which Fujimori and an estimated 90 percent of Peruvians belong.

But Fujimori excluded the evangelicals from his cabinet and has given them practically no role. Second Vice President Carlos Garcia, a Baptist minister, has criticized publicly the government's welfare policies, which he had no power to influence.

Having angered the non-Roman Catholics, Fujimori then proceeded to anger the Roman Catholic hierarchy over birth control. Two weeks ago, he warned that Peru's population was growing too quickly and within a decade could jump from the current 22 million to more than 30 million. His health minister announced plans to distribute free birth-control pills, intra-uterine devices and condoms.

"The upper classes are well informed, but in the popular classes there is disinformation . . . fear and myth," said Fujimori.

The Roman Catholic Church immediately announced its opposition, blasting Fujimori for ignoring "human values and morals." He responded that the church was "restricting the liberty of the citizens with medieval opinions and recalcitrant positions."

It seemed an ill-advised fight for Fujimori to start, but informal polls showed the public backing him over the church. A columnist for a conservative daily noted that in his fights with the judiciary and the church, Fujimori has taken positions that strike a chord with a society long disenchanted with the failures of its leading institutions.

Fujimori has forged close ties with the army, and many observers now see it as one of the new administration's most important bases of political support.

In his inauguration-day decision to remove the chiefs of the navy and the air force, Fujimori was careful to leave the army command alone. He then named an active-duty army general as minister of the interior, giving the army a new measure of control over the rival national police.

Fujimori's cultivation of the army was widely seen as a kind of insurance policy, providing an ally in case his economic adjustment leads to widespread disorder. But despite the hardships the program has caused -- the minimum wage is still only about $60 a month -- there has been no social explosion. Meanwhile, triple-digit monthly inflation has dropped to 10 percent a month.

"People were tired of the instablity that hyperinflation had caused," said Rospigliosi. "After what we went through, monthly inflation of just 10 percent seems like a miracle."

After inheriting an empty treasury, the government now has reserves of about $500 million. Peru has resumed payments on the portion of its foreign debt owed to the World Bank and is negotiating with the International Monetary Fund and other lenders to return to the good graces of the international financial system.

The economy is the issue on which Fujimori may ultimately be judged, but a diplomatic observer said: "He has staked out more than an economic agenda -- it's an agenda aimed at changing some of the ways this society works."