Aug. 22 is a holiday in Russia: It’s Flag Day. But it ranks low in the hierarchy of holidays. There will be no parade, like there is on Victory Day. Russians will not get a day off, like they do on May Day, Russia Day, International Women’s Day, Defenders of the Fatherland Day and a half-dozen other holidays. A visitor to the country would be unlikely to notice that this month Russia is marking the 25th anniversary of a historical milestone.

What happened a quarter-century ago? On Aug. 18, 1991, four top Soviet officials flew to Crimea, where President Mikhail S. Gorbachev of the Soviet Union was on vacation, and placed him under house arrest. The following day Soviet citizens awakened to the news that a committee of K.G.B., military and Soviet Communist Party leaders had declared a state of emergency. Then, over the course of three days, the coup crumbled.

On Aug. 21, its failure became evident, and Moscow authorities soon removed a giant statue of the founder of the secret police, Felix Dzerzhinsky, from its pedestal in the center of the city. A Russian flag — white, blue and red stripes – went up over the building of the Russian Supreme Soviet, the nominal legislative body, in Moscow. Only three people died in Moscow streets before the attempted coup was over.

Two years earlier, a series of popular protests led by young pro-democracy activists had brought down the Communist governments of several Eastern European countries. These became known as the Revolutions of 1989. Most had been peaceful; the Czechs called theirs “velvet.” The ruling parties had simply capitulated. In many books published in the West, and in the minds of some Russian intellectuals, the three days of August 1991 were the Russian version of a velvet revolution, and they have been memorialized as the end of the Soviet Union.