Although still a little-known figure, Yuri Andropov has clearly established himself as the new Kremlin leader.

The extraordinary speed and apparent ease with which he did so contrast with protracted periods of consolidation of power that have characterized previous changes in Soviet leadership. The rapid transition of the past 10 days has thrown into clearer focus Andropov's apparently formidable political skills and the forces that pushed him to the top.

Much of this may have been due to the Kremlin's desire to demonstrate to the world and the Soviet people that a quick and orderly succession after the death of Leonid Brezhnev had brought forward a new and decisive leadership.

Some of it, undoubtedly, is due to Andropov's own desire to consolidate his authority.

Although Andropov was named head of the party and not technically head of state, he threw protocol to the wind in greeting the foreign dignitaries who attended Brezhnev's funeral and conducted negotiations with several key foreign delegations.

Foreign visitors who talked to Andropov this week described him as a forceful man of keen intellect who is at ease in the role of the Soviet leader. As one source put it, "He does not look like a guy who has to turn around to take a vote in the Politburo" on issues he raises with foreign leaders.

On the eve of a meeting of the policy-making Communist Party Central Committee, Andropov has made it amply clear, through the kind of public gestures that provide a window to private political movement here, that he is more than a temporary figure who will carry on the Brezhnev policies until a new strong leader emerges.

The overriding priority for his leadership is to revive the economy and head off what looks like an approaching social and economic crisis. The question is whether he may be broad-minded enough to realize that radical measures are needed even if they infringe on ideology. If so, the other question is whether he has sufficient political stamina to overcome the opposition of entrenched conservatives.

From what little is known about him, the somewhat professorial-looking Andropov has been better prepared for supreme office than any of his four predecessors. With the exception of Lenin, the founder of the Soviet state, he is the first intellectual in this post.

He likes theater and the arts and has written extensively on ideological matters. The 15 years he spent as head of the KGB security police have made him probably the most informed man in the country. In that post he was, in a way, both a foreign and interior minister in charge of a vast organization with foreign and domestic responsibilities.

Apart from its role in suppressing dissent, the KGB also has to supply the Kremlin with sophisticated assessments of trends, ideas, moods and aspirations at home and abroad.

Perhaps the key drawback in his otherwise broad background is the absence of practical experience in economic matters.

Another is his age. At 68 Andropov is the oldest man to take charge of this vast country. Brezhnev and his predecessor, Nikita Khrushchev, were a decade or more younger when they came to power. Lenin died at age 52. His successor, Stalin, was 45 at that time.

Judging by his performance in office so far, Andropov is likely to seek a period of quiet abroad to reassess priorities and reexamine Moscow's commitments.

Rumors are circulating here that he had harbored deep misgivings about Brezhnev's decision three years ago to invade Afghanistan and that he had even offered his resignation from the Politburo. While such rumors lack credibility, the fact they are circulating nevertheless are indicative of fresh intentions here to reassess the Afghan venture.

Andropov publicly signaled this by meeting with Afghanistan's leader, Babrak Karmal, and the leaders of India and Pakistan to discuss the Afghan problem.

While reaffirming that Moscow could not be pushed around by the United States, the new leadership also has made it clear that it will not seek to worsen the already bad relations with the West and that it would seek arms agreements and some measure of detente.

In this situation, in the view of observers, much will depend on the attitude of the Reagan administration and particularly on American positions in the arms negotiations under way in Geneva.

Andropov probably does not have to look over his shoulder at other Politburo members. His most important constituencies are the KGB and the armed forces.

Although he is the country's top leader, Andropov is yet to become its formal commander in chief. He has not served in the Army, but he holds the rank of general of the Army by virtue of his service as chief of the KGB. Unlike Brezhnev, who had the rank of marshal and was chief of the defense council, Andropov has yet to take full charge of this body.

At the moment, Marshal Dmitri Ustinov, the defense minister, and Marshal Nikolai Ogarkov, his deputy, are the ranking figures on the defense council, which is in charge not only of the entire military establishment but also of everything related to it, from transportation to supplies.

An account of Brezhnev's death and the subsequent events leading to the selection of Andropov as party leader illustrates the role of the armed forces and the KGB in the process.

The account, pieced together from various sources, runs as follows:

Brezhnev's death on Nov. 10 was completely unexpected. He and his wife, Viktoria, had breakfast at their dacha in Barvikha. After breakfast, Brezhnev said he had to pick up something in his bedroom and left his wife. When Brezhnev failed to return after about 10 minutes, his bodyguard rushed to the bedroom to find the leader on the floor.

Brezhnev was dead long before the medical team arrived on the scene.

According to various sources, Ustinov and Andropov signed an order alerting military forces in the Moscow region. While Soviet commanders can alert their forces in all other parts of the country, they cannot do so in the Moscow region without the signature of the party secretary. With Brezhnev dead, Andropov, as second secretary of the party, had the authority to sign.

According to these sources, Andropov used the KGB's communication network -- rather than that of the Central Committee -- to alert members of the Central Committee who are not based in Moscow to come to the capital immediately.

Although Andropov's main rival, Konstantin Chernenko, was in control of the Central Committee apparat by virtue of his close association with Brezhnev, Chernenko was cut out of the action from the start.

The crucial selection was made at a meeting of the "leadership" -- up to 50 persons, including Politburo members, alternates and key members of the Central Committee. The backing of the armed forces was decisive. The sources said that Ustinov proposed that the nominating speech should be made by Chernenko to demonstrate unity.

Central Committee members were said to have been briefed in groups about the decision. At the formal meeting on Nov. 12, the committee voted unanimously to elect Andropov as its general secretary.