The signal that it had changed was often the publication of a pseudo-scholarly article that denounced the "falsifications" of the existing version of history.
Here we go again.
Last week, Colonel Sergei Kovalev, the director of the scientific research department at the Institute of Military History, published an article on the website of the Russian Ministry of Defence entitled "Fictions and Falsifications in Evaluating the USSR's Role On the Eve of the Second World War".
He says it was the Poles who started the war in 1939, not the Nazis.
The British and the French were to blame, too, because earlier in 1939 they guaranteed Poland's independence if it stood up to Hitler's demands.
That gave the Poles "delusions of grandeur", unfortunately, and misled them into rebuffing Germany's "very modest" requests.
Germany only made two demands to Warsaw in 1939.
One was the return of Danzig, a German-speaking city that had been separated from Germany by the Treaty of Versailles that ended World War 1.
The other was a German road and rail corridor across the strip of territory (the "Polish Corridor") that gave the Poles access to the Baltic Sea, but separated eastern Germany from the rest of the country.
Col Kovalev is right about one thing.
Hitler's demands were reasonable enough.
By 1939, almost everybody agreed that the Versailles treaty had been wrong to blame World War 1 on Germany and that the five million Germans, whose lands had been handed out to neighbouring countries under that treaty, had been treated unfairly.
But most historians also think that Hitler's demands were just an opening bid.
The conventional wisdom is that Hitler was determined on world conquest from the start and that if Poland had accepted his terms in 1939 it would just have faced further demands not much later.
But the conventional historians may be wrong, for Hitler also offered Poland a secret alliance against the Soviet Union when he made his demands.
Poland's military rulers rejected the whole package, trusting in the Anglo-French guarantee to protect them.
From the day that the guarantee was issued in March 1939, they refused even to discuss it with the Germans.
That may have been a mistake, for when war came in September Britain and France were unable to help them militarily, and Poland was overrun in a month.
But this hardly explains why Col Kovalev blames Poland for causing the war and why the Russian Ministry of Defence put his article on its website.
The reason for that, most likely, lies with its need to rewrite the history of the Nazi-Soviet Pact.
That was the secret agreement of August 1939, in which Germany and the Soviet Union carved up eastern Europe between them.
The Russians got eastern Poland, all of Finland, Estonia, Latvia and Lithuania, and parts of Romania.
The Finns fought back and managed to save most of their country, but all the rest succumbed.
This deal has always been hard for the Russians to defend, especially since the Nazis attacked them two years later anyway.
They usually say they were just trying to win time, but Stalin clearly fooled himself into believing that he had a real deal with the Nazis.
He was recovering almost all the lands that had won their freedom from the Russian empire after World War 1 (and he wasn't interested in the opinions of the residents).
The Soviet secret police killed or deported hundreds of thousands of "politically unreliable" people in the newly conquered territories. (Twenty thousand Polish officers who had surrendered to the Russians were murdered in Katyn Forest to decapitate any resistance movement.)
So it's not surprising that some people in the Baltic states welcomed German troops as liberators in 1941 and that very few people anywhere in Eastern Europe saw Red Army troops as liberators when they came back in 1944.
This has always infuriated the Russians, who see the Red Army as heroes and liberators.
Col Kovalev's article blaming the Poles for the war was bound to appeal to Russian patriots, just as much as it would appal Poles, Estonians and all the other Eastern Europeans who had to live for decades under the Soviet yoke.
The Polish ambassador in Moscow protested and Col Kovalev's article has now been removed from the Ministry of Defence's website, but the broader trend in Russia is clearly to rewrite history in ways that rehabilitate the Soviet past.
Indeed, last month Russian President Dmitri Medvedev ordered the creation of the Commission to Counteract the Falsification of History to the Detriment of Russian Interests.
That sounds slightly less weird in Russian, but not much.
And there's now legislation before the Duma (Parliament) that would outlaw any portrayal of the Red Army as invaders even on the territory of former Soviet Republics.
Of course, Moscow could not enforce that legislation without invading (sorry, liberating) them again, so it has little practical effect, but it is indicative of the mood in the country.
Russia isn't planning to invade anybody but it is feeling spectacularly touchy and grumpy at the moment.
So far, Mr Medvedev (and Prime Minister Vladimir Putin) are managing to ride the tiger, but if they fall off they could be eaten up in a flash.
Gwynne Dyer is a London-based independent journalist.
