The Soviet Union was bound to collapse eventually. But that it collapsed as peacefully as it did 25 years ago this week is largely a tribute to one leader: George H. W. Bush. History will remember America's 41st president for ensuring that so large and authentically historic an event could take place so casually.

Sure, there are other reasons for the demise of the ghastly USSR on Christmas Day 1991: the US defence build-up during the Reagan years, the forces of glasnost and perestroika that Mikhail Gorbachev unleashed, the implosion of central planning, the failure of Marxism-Leninism and the revolt of the republics.

All true. But it was Bush's prudent and cautious response to the revolutionary upheavals from 1989 to 1991 that helps explain why the blood-soaked superpower disappeared almost overnight and with virtually no bloodshed.

The temptation today is to regard all this as inevitable. But it could easily have been so much messier. When empires collapse, brutality and violence usually coincide: think of the British departure from Kenya, Malaya and the Indian subcontinent; or the French from Vietnam and Algeria; or the Belgians from Congo.

What took place in the case of the Soviet Empire's collapse was very much the exception. Why?

The answer lies in recognising that Bush and his senior advisers James Baker, Brent Scowcroft, and Lawrence Eagleburger were deliberate and cautious conservatives, conscious that the dissolution of the totalitarian superpower into 15 separate nations could unleash turmoil and chaos.

Such concerns were especially reasonable given that several successor states, such as Ukraine, held poorly guarded strategic nuclear weapons from the Soviet arsenal that were aimed at the US.

When Eastern Europe was liberated in November 1989, Bush was not in a celebratory mood. Democrats berated him for not dancing on the Berlin Wall. But the president defended his "reserved behaviour" for fear that triumphalism might provoke the Kremlin into cracking down on the revolutionary movements.

In 1990, Bush reached an implicit deal with Gorbachev that in exchange for a unified Germany's inclusion in NATO, the western alliance would not move east. The logic: Bush did not want to exploit Russia's moment of weakness by expanding US security reach into what Moscow had viewed as its near abroad well before Joe Stalin appeared on the scene.

When a diehard communist coup against Gorbachev unfolded in August 1991, Bush was restrained. "We're not going to overexcite the American people or the world," he said. "We will conduct our diplomacy in a prudent fashion, not driven by excess, not driven by extreme." By Christmas 1991, Moscow allowed the Baltic states to separate from the Soviet Union.

US liberals and conservatives have criticised Bush for failing to welcome the end of the Cold War and embrace national self-determination among the Soviet republics more enthusiastically. This was a time when journalists and intellectuals were celebrating the triumph of Western liberal democracy and drawing comparisons between America's global predominance and that of Rome.

In an essay in The National Interest in 1989, Francis Fukuyama proclaimed "the end of History". In another influential essay in Foreign Affairs, Charles Krauthammer called for the US to summon "the strength and will to lead a unipolar world, unashamedly laying down the rules of world order and being prepared to enforce them". 

But the Fukuyama-Krauthammer world-view was alien to Bush, a balance-of-power realist whose low-profile use of US diplomatic and economic leverage over the Kremlin constrained Gorbachev's ability to crack down on nationalist movements in the Baltics.

"I did not want to encourage a course of events which might turn violent and get out of hand," he later said. For Bush, the enemy was unpredictability and instability.

The most striking aspect of the 25th anniversary of the collapse of the Soviet Union is how little coverage it has received. But this week the 92-year-old Bush deserves to be remembered for what he did and, perhaps more importantly, what he refused to do.

It was only after the USSR's collapse when Bush boasted that America had "won" the Cold War through its "biblical" efforts. Which perhaps explains why his successors have indulged in a combination of hubris and naivete.

Although they expressed themselves in different ways, Bill Clinton, George W. Bush and even Barack Obama just assumed that the US, as the world's "indispensable nation," (as Madeleine Albright put it) could extend its strategic reach onto the former Soviet Union's frontiers and offer security guarantees to almost any state that wanted them without ever provoking a Russian backlash.  

There's a useful lesson here for Washington that is presently suffering from a bout of Russiaphobia. Bush was no softie, but he recognised the folly of grinding the face of a defeated foe in the dirt. Russia is a declining power, but history has returned with a vengeance. Moscow has legitimate security interests, and it will play hardball to protect them.

Moreover, if made desperate and humiliated further, Russia could be dangerous like a cornered, wounded animal. And, of course, it maintains enough nuclear weapons to wipe the US off the planet. Better to deal with the bear than needlessly poking at it.

Originally published in The Sydney Morning Herald.