Who remembers Hungary, 1956? Tibet, 1959? Czechoslovakia, 1968?
How about Iraq, 1991? Or Iran, 2009?
I hope the connection is obvious by now: all of them were popular uprisings, and all of them were crushed. In other words, there is no law of nature that says popular protest must always prevail.
Which brings us to Syria. Yesterday marked the first anniversary of the start of the mass protests against President Bashar al-Assad. According to the United Nations, more than 8,000 people have been killed since the protests began.
Over the past three weeks, ever since the anti-Assad rebels staged their "tactical withdrawal" from the Baba Amr district of Homs, the pro-Assad forces have been steadily gaining ground. In both Idlib in the north and Deraa in the south, the two other main centres of anti-Assad revolt, the rebels are under serious pressure.
So am I saying the Syrian uprising is over? No. Am I saying it may well not succeed? Yes. After all, 30 years ago, more than 20,000 people were killed in the Syrian city of Hama, when Bashar al-Assad's father crushed an earlier rebellion by Sunni rebels.
I was in Hama just a few months before the anti-Bashar protests began, and I can tell you there's not much to show for that failed uprising. A beautifully laid-out park marks where the old city centre used to be, before it was flattened, and the ancient "noria" water wheels still creak and turn, as they have done for hundreds of years.
Perhaps we would have felt differently about the Arab spring if it hadn't started in Tunisia and Egypt. It seemed almost easy, didn't it? In Tunisia, the army simply wasn't prepared to fire on its own people; and in Egypt, the generals apparently decided to sacrifice President Hosni Mubarak in order to protect their own position.
For a brief moment, it looked as if Arab autocrats were being swept away like rotting driftwood in a storm. But then came Libya, and Bahrain, and Yemen.
In Libya, NATO stepped in, with UN authorisation, to back the rebels; in Bahrain, the Saudis and their Gulf allies stepped in to back the ruling family. In Yemen, months of painfully protracted negotiations finally engineered the removal of President Ali Abdullah Saleh, although how much of a real change there has been remains to be seen.
So why do some uprisings succeed while others fail? On the evidence of the past year, I'd suggest two crucial elements are in play: the readiness of the old regime to deploy overwhelming military force, up to and including the use of heavy weapons such as tanks and artillery in residential areas; and the involvement of neighbours and regional powers.
In Libya, the old regime was prepared to use overwhelming force, but outside powers (NATO, Qatar) backed the rebels. Result: the rebels won. In Syria, the regime is certainly prepared to use even more overwhelming force, but so far, outside powers (Qatar, Turkey) are providing only limited aid to the rebels. Result: the rebels have not won.
Whether it's Budapest or Prague, Lhasa or Basra, military might wins the day. There have, of course, been many other uprisings which toppled autocratic regimes without a shot being fired. The ripple of European revolutions that marked the end of the Cold War in 1989 showed us what happens when sclerotic regimes rot from within and lose the will to hang on to power.
But that's not what we're seeing in Syria. President Assad's father crushed the revolt in Hama and went on to rule for another 18 years, before dying peacefully in his bed. Bashar's rule is not universally unpopular (there has been relatively little protest in either the capital, Damascus, or in Syria's second city, Aleppo), and there is no evidence to suggest that his regime has lost the will to live.
The word from Washington, London and other Western capitals is that it's only a matter of time before the regime is toppled. Maybe so, but history suggests that's not necessarily the inevitable outcome.