Back in the Gorbachev era, the Russian state actually apologized for the U.S.S.R.’s role in these atrocities. In 1989, the Soviet Congress of People’s Deputies even declared the Molotov-Ribbentrop Pact null and void. But the mood has been changing for some time. Academic defenses of the Hitler-Stalin alliance began appearing again in Russia in 2009, timed to the 70th anniversary of 1939; one collection of essays published at the time even included an approving introduction written by Sergei Lavrov, the Russian foreign minister.

Events of this year, which marked the 80th anniversary, may also have reinspired the Russian president. In September, the European Parliament passed a resolution condemning the pact, as well as the two totalitarianisms that destroyed so much of Europe in the 20th century. That kind of statement rankles Putin, who now holds annual celebrations of World War II Victory Day and uses the war as one of the symbolic justifications for his own authoritarianism. He wants to make Russia not just great again, but “great” precisely as it was “great” in 1945, when the Red Army occupied Berlin.

But that was three months ago. Why stir trouble? Why create bad blood exactly now? After all, things are going rather well for Putin, at least in his relations with the Western world. The American president is a fan; pro-Russian, far-right political parties are thriving in Germany, Italy, Austria, and France; even moderate Europeans are tiring of the chilly relationship with Russia and are bored with sanctions. Poland, meanwhile, is more isolated than it has been in 30 years. The unique Polish-German relationship, built up over several decades, has been almost totally destroyed by the current populist, nativist Polish government, some of whose members are more anti-European than anti-Russian. More tension is coming. Having packed the constitutional court, the Polish Parliament is now preparing, this month, to vote on a law that could allow the government to fine, or even fire, judges who question the government’s judicial reform, or engage in any political activity at all. This illegal, unconstitutional assault on judicial independence, as well as on judges’ civil rights, will almost certainly bring Poland once again into conflict with its allies.

But maybe, from Putin’s point of view, that makes this a good moment to launch a verbal attack on Poland. The nation is no longer quite so integrated, no longer quite so automatically European, no longer able to count on good German friends—maybe this is an excellent time for the Russian president to cast doubt on Polish history, too. Or, as we have all now learned to say, maybe it is a good moment to cast doubt on Poland’s “narrative”: Victim of the war, victim of communism, triumphant fighter for democracy and freedom—all of that can be thrown into doubt. Later this month, Putin will be the main speaker at an Israeli event to mark the 75th anniversary of the Red Army’s liberation of Auschwitz, and that will be another moment to make the same argument. It’s also a good way to test the waters. Just as Poland is on the threshold of a move in the direction of real authoritarianism, Putin wants to see how the world reacts—how Poland reacts—to the idea that Poles and Nazis were more or less the same thing.