For many people the sight of Russian tanks streaming across a border in August has uncanny echoes of Prague 1968. That cold war reflex is natural enough, but after two decades of Russian retreat from those bastions it is misleading. Not every development in the former Soviet Union is a replay of Soviet history.

The clash between Russia and Georgia over South Ossetia, which escalated dramatically yesterday, in truth has more in common with the Falklands war of 1982 than it does with a cold war crisis. When the Argentine junta was basking in public approval for its bloodless recovery of Las Malvinas, Henry Kissinger anticipated Britain's widely unexpected military response with the comment: "No great power retreats for ever." Maybe today Russia has stopped the long retreat to Moscow which started under Gorbachev.

Back in the late 1980s, as the USSR waned, the red army withdrew from countries in eastern Europe which plainly resented its presence as the guarantor of unpopular communist regimes. That theme continued throughout the new republics of the deceased Soviet Union, and on into the premiership of Putin, under whom Russian forces were evacuated even from the country's bases in Georgia.

To many Russians this vast geopolitical retreat from places which were part of Russia long before the dawn of communist rule brought no bonus in relations with the west. The more Russia drew in its horns, the more Washington and its allies denounced the Kremlin for its imperial ambitions.

Unlike in eastern Europe, for instance, today in breakaway states such as South Ossetia or Abkhazia, Russian troops are popular. Vladimir Putin's picture is more widely displayed than that of the South Ossetian president, the former Soviet wrestling champion Eduard Kokoity. The Russians are seen as protectors against a repeat of ethnic cleansing by Georgians.

In 1992, the west backed Eduard Shevardnadze's attempts to reassert Georgia's control over these regions. The then Georgian president's war was a disaster for his nation. It left 300,000 or more refugees "cleansed" by the rebel regions, but for Ossetians and Abkhazians the brutal plundering of the Georgian troops is the most indelible memory.

Georgians have nursed their humiliation ever since. Although Mikheil Saakashvili has done little for the refugees since he came to power early in 2004 - apart from move them out of their hostels in central Tbilisi to make way for property development - he has spent 70% of the Georgian budget on his military. At the start of the week he decided to flex his muscles.

Devoted to achieving Nato entry for Georgia, Saakashvili has sent troops to Iraq and Afghanistan - and so clearly felt he had American backing. The streets of the Georgian capital are plastered with posters of George W Bush alongside his Georgian protege. George W Bush avenue leads to Tbilisi airport. But he has ignored Kissinger's dictum: "Great powers don't commit suicide for their allies." Perhaps his neoconservative allies in Washington have forgotten it, too. Let's hope not.

Like Galtieri in 1982, Saakashvili faces a domestic economic crisis and public disillusionment. In the years since the so-called Rose revolution, the cronyism and poverty that characterised the Shevardnadze era have not gone away. Allegations of corruption and favouritism towards his mother's clan, together with claims of election fraud, led to mass demonstrations against Saakashvili last November. His ruthless security forces - trained, equipped and subsidised by the west - thrashed the protesters. Lashing out at the Georgians' common enemy in South Ossetia would certainly rally them around the president, at least in the short term.

Last September, President Saakashvili suddenly turned on his closest ally in the Rose revolution, defence minister Irakli Okruashvili. Each man accused his former blood brother of mafia links and profiting from contraband. Whatever the truth, the fact that the men seen by the west as the heroes of a post-Shevardnadze clean-up accused each other of vile crimes should warn us against picking a local hero in Caucasian politics.

Western geopolitical commentators stick to cold war simplicities about Russia bullying plucky little Georgia. However, anyone familiar with the Caucasus knows that the state bleating about its victim status at the hands of a bigger neighbour can be just as nasty to its smaller subjects. Small nationalisms are rarely sweet-natured.

Worse still, western backing for "equip and train" programmes in Russia's backyard don't contribute to peace and stability if bombastic local leaders such as Saakashvili see them as a guarantee of support even in a crisis provoked by his own actions. He seems to have thought that the valuable oil pipeline passing through his territory, together with the Nato advisers intermingled with his troops, would prevent Russia reacting militarily to an incursion into South Ossetia. That calculation has proved disastrously wrong.

The question now is whether the conflict can be contained, or whether the west will be drawn in, raising the stakes to desperate levels. To date the west has operated radically different approaches to secession in the Balkans, where pro-western microstates get embassies, and the Caucasus, where the Caucasian boundaries drawn up by Stalin, are deemed sacrosanct.

In the Balkans, the west promoted the disintegration of multiethnic Yugoslavia, climaxing with their recognition of Kosovo's independence in February. If a mafia-dominated microstate like Montenegro can get western recognition, why shouldn't flawed, pro-Russian, unrecognised states aspire to independence, too?

Given its extraordinary ethnic complexity, Georgia is a post-Soviet Union in miniature. If westerners readily conceded non-Russian republics' right to secede from the USSR in 1991, what is the logic of insisting that non-Georgians must remain inside a microempire which happens to be pro-western?

Other people's nationalisms are like other people's love affairs, or, indeed, like dog fights. These are things wise people don't get involved in. A war in the Caucasus is never a straightforward moral crusade - but then, how many wars are?

· Mark Almond is a history lecturer at Oriel College, Oxford mpalmond@aol.com