The defiance shown by Muscovites that night was defiance of a different quality from that of the pro-democracy demonstrators who had regularly massed in central Moscow on Saturdays through the previous year.
Now, in place of mostly passive riot police, serious military hardware threatened. Tanks and armoured personnel carriers had encircled the city; they now surrounded the White House in what could quickly become battle formation.
A curfew had been declared. The crowd were risking their lives. In that single act, in that single evening, they shattered the power of the Communist Party and the KGB that did its dirty work. The spell of repression was broken.
The next day, the downcast eyes and neutered expressions so characteristic of people who live in fear had gone; just like that. And, contrary to the alarms that have been sounded so often since, in 20 years, that all-pervasive fear has never returned.
For Russians, it had been a long day; one of the longest perhaps in the history of the Soviet Union.
I had been woken by a call from an Australian radio station, asking for verification of a report that the Soviet President, Mikhail Gorbachev, had resigned for health reasons and transferred power to a self-styled Emergency Committee. Heading the list of names was that of Gennadi Yanayev, the vice-president Gorbachev had been pressed by his hardline opponents to appoint.
All state television and radio stations were broadcasting Swan Lake, regularly interrupted by the new committee's official declaration of emergency.
At 9am I had watched as the rush-hour traffic dodged an interminable column of tanks and armoured personnel carriers (APCs), rumbling into the centre of town. An hour later, I had set off with my driver, Kolya, to try to find out how effectively the state of emergency was being enforced.
We drew up in front of the Parliament in time to see more tanks and APCs manoeuvring into position. Eventually, Yeltsin emerged from the building.
He had levered his great frame up on to the tank - producing the pictures that sped around the world (but not Russia) - and delivered the forthright statement that established his place in history. Categorically rejecting the coup, he warned: "The clouds of terror and dictatorship are gathering over the whole country. They must not be allowed to bring eternal night."
Late afternoon had produced the infamous press conference by members of the emergency committee, noted at the time for Yanayev's trembling hands, but also for the challenge from a young Russian reporter.
Tatyana Malkina challenged the right of the committee to take power. "Could you please say," she asked, "whether or not you understand that last night you carried out a coup d'etat?"
The question drew gasps from those present; in other circumstances it could have cost her her life.
Each of these actions by itself - Yeltsin's public defiance; the tank command's refusal to intervene; the young journalist's fearlessness - was decisive in its own way.
But what turned the tide of history was the resistance of those ordinary Muscovites who trudged to the White House in the perhaps naive faith that they could fend off the tanks and protect "their" President.
As it happened, they were right. The fate of the Soviet Union and of Russia hung in the balance that night. The tussle for power was to continue for another two days. Veterans of the Afghan war built barricades, in an attempt to thwart the tanks.
But after that first night, Yeltsin had the upper hand. On the Wednesday, the plotters bowed to the inevitable and a plane was dispatched to the Crimea - where the Gorbachev family had been held at the presidential villa - to bring the Soviet leader back to Moscow.
In a particularly spiteful piece of theatre, Yeltsin forced the Soviet leader to sign the all-powerful Soviet Communist Party out of existence. In truth, though, the form in which it had held sway for more than 70 years had dissolved itself. And the Soviet Union was already breaking apart.
Through that autumn, the institutions of state passed one by one from central Soviet to Russian control, from the fading Gorbachev to an ebullient Yeltsin, leaving the Soviet Union a rattling and dysfunctional shell.
On December 8, Russia, Ukraine and Belarus - the original signatories - renounced the treaty that had brought the Soviet Union into being. By a quirk of fate, this was one day before European leaders concluded the Maastricht Treaty. As Europe moved together, the Soviet empire span apart.
On Christmas Day, Gorbachev announced his resignation and accepted the dissolution of the world's second superpower.
Thus ended, mostly peacefully, a system that had been born in chaos and blood 74 years before. And the worst fears - of famine, civil war, a million refugees - went unrealised. The undoing of the Bolshevik revolution was accomplished more benignly than many had feared.
Vladimir Putin, in presiding, first as President, then as prime minister, over 10 years that might be described as the great settling-down, has given Russians the breathing space that an exhausted nation needed.
After three score and 10 years of communism in various guises, and the traumas of World War II and the prison camps, it should astonish no one that Russia has taken that long to start feeling comfortable in its new skin.
It was Gorbachev who banished the fear and precipitated the end of Soviet communism.
It will be the children and grandchildren of those who defied the tanks on August 19, 1991, who will enable Russia to take its rightful place as a law-governed democracy in the modern world.
- INDEPENDENT