Throughout the past decade, it has been an article of faith in the west that the implosion of the Soviet Union represented a liberation for its people and an undiluted boon for the rest of the world. At a stroke, the evil empire had been miraculously swept away and the ground laid for a great leap forward to freedom, peace and prosperity.

There was rejoicing across the political spectrum, from free-market conservatives to the far left. The nuclear threat had lifted and a new world order of democratic global governance had been inaugurated.

History had come to an end and the long-suffering east European masses would at last be able to step out from under the communist yoke to enjoy the liberal capitalism (or genuine socialism, in the leftist version) which was to be the fortunate lot of all humankind.

This weekend, it will be 10 years since the comic opera coup which precipitated the downfall of Mikhail Gorbachev, the banning of the Soviet communist party and the dissolution of the USSR. As the dust and debris have cleared from the convulsive events of 1989-91, the real nature of what they brought about has come into focus.

For all the action on the streets, the changes were mostly engineered by sections of the nomenklatura that realised the old system was in crisis and saw the opportunities for enrichment.

Far from opening the way to emancipation, these changes led to beggary for most citizens, ushering in the most cataclysmic peacetime economic collapse of an industrial country in history. Under the banner of reform and the guidance of American-prescribed shock therapy, perestroika became catastroika.

Capitalist restoration brought in its wake mass pauperisation and unemployment; wild extremes of inequality; rampant crime; virulent anti-semitism and ethnic violence; combined with legalised gangsterism on a heroic scale and precipitous looting of public assets.

The scale of the social disaster that has engulfed the former Soviet Union and much of eastern Europe in the past 10 years is often underestimated outside, or even by visitors to Moscow and other relatively prosperous cities in the former Soviet bloc.

Some of the more startling facts are set out by US Russian studies professor Stephen Cohen in his book Failed Crusade, a savage indictment of western blindness to what has been inflicted on the one-time communist world.

By the late 1990s, national income had fallen by more than 50% (compare that with the 27% drop in output during the great American depression), investment by 80%, real wages by half and meat and dairy herds by 75%. Indeed, the degradation of agriculture is, Cohen argues, in some respects worse even than during Stalin's forced collectivisation of the countryside in the 1930s.

The numbers living below the poverty line in the former Soviet republics had risen from 14m in 1989 to 147m even before the 1998 financial crash. The market experiment has produced more orphans than Russia's 20m-plus wartime casualties, while epidemics of cholera and typhus have re-emerged, millions of children suffer from malnutrition and adult life expectancy has plunged.

As this human tragedy was unfolding, western politicians and bankers harried Russia's leaders to push ahead more energetically with the "reform" and privatisation treatment producing it: a transition in many areas to a premodern age.

Only with the rise in oil prices, devaluation of the rouble and the merciful departure of Boris Yeltsin has the economic slide begun to be reversed. And in eastern Europe, only star performers like Poland have managed to return to the output levels achieved before 1989 - and even then at a cost of millions of unemployed, widespread poverty and social regression.

Some who have championed the lurch from a centralised, publicly owned economy to the robber-baron capitalism of today's Russia will doubtless comfort themselves with the thought that the grim figures exaggerate the costs of change and ignore the greater freedom, democratic structures and better quality of goods now available.

But those freedoms and competitive elections - heavily circumscribed as they are - were largely the fruit of the Gorbachev era and predate the Soviet collapse, while for most Russians and other former Soviet citizens, the wider range of goods are priced out of reach.

That is why people who lived in conditions of full employment, with low housing and transport costs and access to basic health and social provision, mostly tell opinion pollsters they are now worse off than under communist rule. It's hardly surprising in the circumstances that 85% of Russians regret the dissolution of the Soviet Union.

Similalry Leonid Brezhnev - Soviet leader in the 1970s, known as the era of stagnation, but also a period when living standards were rising - was picked out as the outstanding Russian politician of the 20th century.

Russians have seen their country reduced from a superpower to a nuclear-armed basket case in a decade and hatred of the west has grown as its role in that process has been rammed home. For the rest of the world, the impact of the Soviet abdication a decade ago has been no less profound. The removal of the only state that could challenge the power of the US militarily, even if it bled itself white by doing so, drastically narrowed the room for manoeuvre for everybody else.

The winding down of nuclear and strategic confrontation under Gorbachev allowed states like Britain to cut military spending, but also created the conditions for untrammelled US power in a unipolar world, while potentially more volatile nuclear threats emerged.

It is difficult to imagine the Gulf war of 1991 and the subsequent throttling of Iraq or the dismemberment and inter-ethnic wars of Yugoslavia taking place, let along Bush's current rush to unilateralism, if the Soviet Union had not been on its knees or extinct.

For developing countries, in particular, the destruction of the second superpower - which had championed the anti-colonial movement and later the third world cause - largely closed off the scope for different alliances and sources of aid and sharply increased their dependence on the west.

Throughout the world, the removal of the ideological challenge represented by the Soviet Union dramatically weakened the labour movement and the left - and even confidence in political ideas of any kind, something that is only now beginning to change.

Perhaps it is still too early, as the Chinese communist leader Zhou Enlai said of the French revolution, to make a considered assessment of the 70 years of Soviet power: its achievements, failures and crimes, its legacy to progressive politics and the search for an alternative social model.

The particular form of society it created will never be replicated, nor will the conditions that gave rise to it. But the effects of its destruction will be with us for decades to come.

Failed Crusade, Stephen F Cohen (WW Norton)

s.milne@theguardian.com