Gorbachev's stronger hand. The swift shake-up in Moscow once again has demonstrated Gorbachev's mastery of political timing and strategy. Pro-reformists are relieved at the removal of key obstacles.

``A real political victory,'' is how a senior official of the Soviet Communist Party sums up the palace revolution that has taken place in the Kremlin in recent days. In a series of deftly engineered moves, four Politburo members were removed, the influence of Yegor Ligachev, the conservative, second-ranking Soviet leader, was sharply reduced, and Mikhail Gorbachev was made President, a position soon to be vested with wide-ranging powers. (Details of personnel changes on back page.)

``Our political capital was running out,'' the official said, explaining the reasoning behind Friday's and Saturday's actions. ``Everyone knew that perestroika [restructuring] was spinning its wheels. The people's belief in reforms was hanging by a very thin thread.''

Reformist leaders apparently believed that two tightly-connected moves were necessary to galvanize perestroika: Speed up the pace of reform and dump Mr. Ligachev. Both aims were achieved, they feel, even though Ligachev remains in the policy-setting Politburo.

It now seems clear that the main reason for the abrupt timing of the plenum was strategic: Ligachev was coming to the end of his vacation. Once he was back in Moscow, it would have been harder to spring a surprise plenum. Reformers worked fast and effectively. Some Central Committee members heard about the plenum - planned for Friday - only the preceeding Monday. Others apparently heard later. As a result, the official noted, ``Ligachev did not have time to consolidate his forces.''

The announcement of a Central Committee meeting triggered a wave of intense excitement within the party. By Wednesday, the official recalls, hints of high-level changes were circulating. Some were convinced Ligachev would be dismissed.

By this time, the atmosphere in the spacious offices of the official quoted here was electric. Rumors circulated in the building that Ligachev was out.

``Now perhaps we have a chance,'' one lower-level worker commented.

The senior official was less sure. Ligachev's removal would be a major - but very difficult - achievement, the official said at the time. ``For the time being he has very strong political forces behind him.''

What are these forces, he was asked. ``Very many of the Russian federation's regional first secretaries,'' he replied.

Who else backed Ligachev, he was asked. He paused. ``I don't think the armed forces,'' he said, stressing the word think. ``Gorbachev chose [Defense Minister Dmitry] Yazov himself. And I don't think the KGB.''

Contacted again after the results of the Central Committee meeting were known, the official said that Ligachev was ``in essence'' out of power. Ligachev's influence had been drastically curtailed, and that of his main rival, Alexander Yakovlev, considerably strengthened, he said.

``Many of us would have preferred to see Yakovlev handling ideology,'' he said. ``But that would have been too blatant,'' and might alienate more conservative party leaders. He added, however, that Yakovlev would probably dominate ideology as well as foreign policy. ``Yakovlev is a more powerful personality, and will already be handling the foreign policy aspects of ideology,'' he concluded.

Having lost ideology, traditionally the preserve of the leadership's second secretary, Ligachev has now been reduced to overseeing agriculture. His influence in this area may be further limited, party sources say, by the fact that he may share responsibility with the Politburo's agricultural specialist. Still, agricultural policy is of vital importance, and Ligachev could slow down key reforms if he desired.

One important indicator of Ligachev's strength will be whether he continues to chair the Central Committee Secretariat, the top leadership's key administrative body. The official quoted here predicts Ligachev will soon lose this position. During Ligachev's vacation the Secretariat minutes were signed by Gorbachev or Ligachev, he said. But he refused to exclude the possibility that Yakovlev had, in fact, chaired the body.

It is not clear when Gorbachev decided to move against Ligachev. What is clear is why he decided to move.

``As long as Yegor was there the bureaucracy felt safe,'' the official said. ``They thought they could continue to ignore change. They thought that the reform wave would pass.''

The official guessed that Gorbachev's views had crystallized at last June's party conference. ``The conservatism of the delegates was obvious. It was clear that they were not supporting reforms, they were supporting him because he was batyushka [big daddy, the boss].''

Said another reformer: ``For every move by us, there was a half-move from [Ligachev]. We were losing time. Time has become vitally important.''

Some of the changes have been in the pipeline for several months. In late June, a Central Committee member told this correspondent that the four Politburo members just dropped would have difficulty handling the new style of leadership. Late this summer, Viktor Chebrikov, the KGB head, reportedly hinted in a private conversation that he would be leaving his post in October. In mid-September political commentator Fyodor Burlatsky, whose printed views often prefigure Gorbachev's actions, hinted it was time for Mr. Chebrikov and Soviet President Andrei Gromyko to go.

Gromyko has been let down gently, though he hinted strongly that he was not leaving totally of his own volition. Chebrikov, who like Mr. Gromyko was instrumental in getting Gorbachev elected party leader in 1985, has been moved sideways. Some party sources say much of Chebrikov's new job - which includes supervision of the judiciary and the KGB - will in fact be duplicated by Gorbachev's close associate, Anatoly Lukyanov. Chebrikov, too, is moving decorously towards retirement, they suggest.

Who's in, who's out among Soviet leaders

Soviet personnel changes include:

Mikhail Gorbachev replaces Andrei Gromyko as chairman of the presidium of the Supreme Soviet, or President. The office, until now largely honorific, will become the focus of power under planned reforms.

Anatoly Lukyanov, Mr. Gorbachev's contemporary at Moscow University law faculty, becomes first vice-president. Soviet sources say his main task will be to steer political and constitutional reforms, which Gorbachev said will be discussed in November, through the Supreme Soviet (parliament).

Vladimir Kryuchkov becomes KGB chief. Previously first deputy KGB chairman, in charge of foreign intelligence, he has a strong interest in the US: In a recent book, author David Wise says Kryuchkov is CIA defector Edward Lee Howard's ``patron.''

Communist Party leadership: Vadim Medvedev becomes a full Politburo member. New candidate (nonvoting) members are Mr. Lukyanov, Interior Minister Alexander Vlasov, Alexandra Biryukova.

Viktor Chebrikov leaves KGB and joins Central Committee Secretariat.

Boris Pugo, party chief of the Baltic Republic of Latvia, takes over the Control Commission, the party's internal watchdog body.

Party reorganization. The size of the Central Committee apparatus will be halved, party sources say. Six new commissions announced Friday will probably form the basis of a streamlined apparatus. They are: Party Building and Cadre Policy, headed by Georgi Razumovsky; Ideology, Vadim Medvedev; Social and Economic Policy, Nikolai Slyunkov; Agricultural Policy, Yegor Ligachev; International Policy, Alexander Yakovlev; Legal Affairs, Viktor Chebrikov.

Dropped from Politburo: Andrei Gromyko, Mikhail Solomentsev, Vladimir Dolgikh, Pyotr Demichev.