Suppose the president of the United States didn't show up for his annual State of the Union address - and offered no explanation why. That is about the closest comparison that can be drawn with the failure of Soviet leader Yuri Andropov to appear at this year's annual Red Square military review and parade, which occurred on Monday. The event took place under clear blue skies on a crisp, early winter morning in the Soviet capital.
Mr. Andropov's absence has inevitably fueled speculation about the state of his health, since he has not been seen by foreign diplomats or journalists since mid-August.
If he is ill or incapacitated, it would come at a critical time for the Kremlin. Relations between Moscow and Washington are at one of the lowest points since the cold war.
The Soviet Union is trying desperately to block the deployment of new American missiles in Western Europe. And it is trying to capitalize on what it sees as an American misstep in Grenada.
Too, the Soviet Union is facing formidable economic challenges at home. Its economy is hamstrung by the excesses of central planning and widespread corruption. And, since he has been in office for only a year, Mr. Andropov has not been able fully to consolidate his power over the Kremlin bureaucracy and address these problems. Now his health may be complicating matters further.
Mr. Andropov's absence has inevitably sparked speculation among Western observers here. While most agree that it is premature to speculate on a successor, few have been able to resist anyway.
One possible successor is Grigory V. Romanov, 60, a Politburo member since 1976. Mr. Romanov addressed a rally at the Kremlin on Saturday - a high honor for a Politburo member. Known as something of a hard-liner, Mr. Romanov said the international climate today had not been so tense since World War II. He renewed Kremlin threats to retaliate against the deployment of cruise and Pershing II missiles in Western Europe, scheduled to begin in December.
The other front-runner, according to analysts here, is Mikhail Gorbachev, at 52 the youngest member of the Politburo. He is an agricultural specialist, though he has apparently been given expanded duties in the Politburo during recent years.
Some observers, however, play down any notion of impending change in the Kremlin hierarchy. They note that, notwithstanding Mr. Andropov's failure to appear in public, there are a number of signs suggesting that he is still at the helm of the Communist Party and, therefore, the country.
A number of important foreign policy pronouncements have been made in Andropov's name recently. And at a diplomatic reception after the Red Square ceremonies, Soviet Prime Minister Nikolai Tikhonov welcomed the assembled ambassadors in Andropov's name, and made several references to him. Among Kremlin-watchers, such nuances of language are fraught with meaning. In simple language, they mean that Mr. Andropov is still in charge.
However, Mr. Andropov's failure to appear at the Nov. 7 ceremonies is highly unusual. The event - marking the 66th anniversary of the Russian Revolution - is perhaps the single most important event of the Soviet political year. Even the former Soviet leader, Leonid Brezhnev, reviewed last year's ceremonies just days before he passed on.
The Kremlin, meanwhile, has given few clues as to the reasons for Mr. Andropov's absence. And what few there have been came forth in Byzantine fashion. Last week, a letter from Mr. Andropov to a physician's group mentioned that he had a cold. It was reprinted in Soviet publications - the first time in memory that a Soviet leader's ill health has been the subject of press accounts.
Mr. Andropov's absence from the group was not entirely unexpected, however. Leonid Zamyatin, chief of the Communist Party Central Committee's International Information department, told Western journalists on Saturday that Mr. Andropov probably would not be at the ceremonies. But his comments came during a chance encounter with newspeople, not as part of any official announcement.
No explanation for his absence has been offered to the Soviet public. Tass, the official Soviet news agency, merely reported that ''leaders of the Communist Party and the Soviet state . . . were at the main platform of the Lenin Mausoleum'' - without mentioning that Mr. Andropov was not among them.
The Red Square parade is a rich form of political theater. It is an opportunity for the Kremlin to demonstrate to its own citizens and its allies that it has substantial military might, as well as air Communist Party views on foreign policy.
Some observers were struck by how harshly the US was treated in the commentary on the floats and banners. One float showed a caricature of Reagan, wearing a cowboy hat, astride a missile. A Soviet hand was restraining the projectile.