The selection of Yuri Andropov as Central Committee secretary is one of the most favorable developments to have occurred in the Soviet Union in recent years. It is yet another strong piece of evidence that the Soviet succession will being significant reform fairly quickly rather than after a long transitional period.

Andropov, chairman of the KGB for 14 years, is primarily known in the West as head of the secret police, which has been suppressing dissidents. That is an important part of his responsibilities and of his personality. He has recently spoken out forcefully against a multi-party system, and, as a national leader, he would likely be as harsh on the dissidents as Leonid Brezhnev.

Yet the degree of success of the dissidents is not the whole story of the evolution of Soviet society. If we focus upon political struggles and trends within the Soviet Communist Party, Andropov is an extremely interesting figure.

Two facts are crucial. First, the KGB has foreign intelligence and foreign policy responsibilities as well as internal security ones. Andropov's background suggests he was chosen predominantly for the first set. For the 14 years before becoming KGB chief, Andropov worked in the foreign policy realm. From 1953 to 1957, he was ambassador to Hungary, and from 1957 to 1967 head of the Socialist Countries Department of the Central Committee.

The key deputy chairmen of the KGB for internal security were Brezhnev cronies, and Androprov cannot have had much control over them. He surely spent much of his time in the KGB's foriegn policy realms.

Because of his ambassadorship in Hungary, he must have remained the leadership's special expert on that country, and it is difficult to imagine the Soviet Union tolerating and increasingly approving the reforms that have been carried out in Hungary if Andropov had not been pushing that line.

The second key fact about Andropov is that he is a protege of Otto Kuusinen, the old Soviet leader of Finnish extraction. From 1940 to 1951, Andropov did Komsomol and party work in the Karelo-Finnish republic under Kuusinen, who, as he rose in influence in the Khrushchev period, took Andropov with him.

Kuusinen is known in the West as the man Stalin tried to install as Communist leader in Finland during the Soviet-Finnish War of 1939-1940. But within the Soviet Union he was an important reformist figure. As Comintern secretary in 1934, he argued against Stalin in favor of the establishment of the Popular Front against Hitler. In 1945-1946, under the pseudonym of "N. Baltiisky," he wrote favorably about West European socialists at a time when this suggested detente, and in one remarkable article in 1945 he even seemed to advocate, in an Aesopian way, independence for Poland.

Once Stalin died, Kuusinen became an important adviser in Moscow, and in 1957 he was named a Central Committee secretary and a full member of the Presidium.

Essentially Kuusinen was a reformist, non-dogmatic ideologist, who served as a counterpoint to the more conservative Mikhail Suslov. To head his full-time "group of consultants," he chose the 30-year-old Fedor Burlatsky, an intellectual who had been the most outspoken advocate of democratization and de-Stalinization in the Soviet media in 1954-57.

When Kuusinen died, the group of consultants was divided into two -- one for the International Department and one of the Socialist Countries Department. The Kuusinen group essentially was given to the Socialist Countries Department, that is, to Andropov. Andropov soon replaced Burlatsky as its head with another of its members, George Arbatov, now the director of the Institute of the U.S.A. and Canada.

Arbatov continued in this post until 1967. The group included a number of important reformist intellectuals -- notably Alexander Bovin, now the Izvestia columnist, and Oleg Bogomolov, the director of the institute that studies East European economic reform.

No leader accepts all the ideas of his advisers, but Andropov surely was aware of Arbatov's public role of pushing detente since 1954 when he selected him as his chief long-term adviser.

Andropov's most recent speech, on the anniversary of Lenin's birthday, suggested that he is still thinking in these terms. Its two major themes were the creative nature of Marxism-Leninism (a code-word for the need to modify it) and the absolutely central character of the question of peace and war. Andropov was forthright in stating that the Soviet Union must get on with solving its own problems.

Andropov is probably now the heir apparent, and, if this is the case, Arbatov may become his national security adviser. But all of the candidates have weaknesses in their background, and the new leadership is likely to be collective and to resemble that of 1953-1957 in which important reform occurred, including a limitation on the growth in military budgets. The Reagan administration should be prepared to respond.