September 17 is one of these orphan anniversaries that no one wants to claim. It is too shameful to celebrate for some and too uncomfortable to commemorate for others. Many would rather not have to confront this date, yet confront it they must.

Seventy years ago, in the morning hours of September 17, 1939, the Red Army troops crossed the Polish border and over the following weeks, in accordance with the secret protocols of the Ribbentrop-Molotov Pact, occupied and annexed large swathes of what was then eastern Poland and is now western Ukraine and Belarus and southern Lithuania. The outgunned and outmaneuvered Polish army was already by that stage collapsing under the onslaught of the first German blitzkrieg, so from a military point of view the Soviet invasion did not materially affect the outcome of the struggle. It did, however, provide a dastardly coup de grace for the first chapter of the Second World War.

But don’t expect much news and commentary about September 17; not in the West, and certainly not in Russia.

The anniversary is an uncomfortable reminder that for around one third of the duration of the war, the Soviet Union was one of the aggressors — first against Poland, then against Finland, and finally against the Baltic states and Romania — and that during that time it provided invaluable material aid to further the Nazi aggression against the West, while at the same time committing mass war crimes within the newly occupied territories, of which the so called “Katyn massacre” of some twenty thousand Polish army officers taken prisoner of war is only the most widely known.

Very few others have been investigated, none have been prosecuted (if one excludes the farcical attempt by the Soviets to pin the blame for Katyn on the Germans during the Nuremberg trials), and not one person responsible has ever been held to account. To add insult to injury, the very memory of the Soviet atrocities committed east of the Ribbentrop-Molotov line had been banished and criminalized after the war, right up until the fall of the Berlin Wall. For years, September 1, not the 17th, was the only date to remember, and for many it remains the only date that matters and the only date they know.

The commemorations of the start of the Second World War, held in Gdansk, Poland, on September 1, have been a rather somber and understated affair. Ironically, the most prominent international attendees were Angela Merkel and Vladimir Putin, representing the two original aggressors. Great Britain and France sent their foreign ministers, Miliband and Kouchner. The United States sent merely the National Security Adviser, Jim Jones, and only after the outrage at the unseriousness of the initial choice, former Clinton Defense Secretary William Perry.

Contrast this with the 60th celebration of the end of the Second World War a few years ago, a poignant yet triumphant occasion which mixed inspirational pageantry with the celebration of the triumph over evil (well, one of them, in any case) and the victory of democracy (west of the Iron Curtain). But no one particularly likes to remember the start of wars, least of all this one.

For Poland it is a reminder of another dark age in its history. For Germany it is a reminder of its aggressive past. For Great Britain and France it elicits an uncomfortable realization that despite the security guarantee given to Poland months before the outbreak of war, all the aid by the Western allies consisted of air-dropping leaflets across the German border. Lastly, for Russia, it is a reminder of its own shameful role in the drama, and perhaps more importantly, of the continuing inability to come to terms with its past. No wonder that the Gdansk commemorations have received only perfunctory news coverage and no usual outbreak of the “greatest generation”-type commentary.

I am not a great believer in historical apologies. I hold a rather unfashionable view that only those personally responsible for actions or inactions can truly be and say they are sorry, and that the sins of the fathers should not be visited on their progeny. But this is not to say that moral judgments cannot be made about the past. Far from it. I did not want Vladimir Putin to come to Gdansk and apologize and abase himself for Stalin’s actions seven decades ago, but I would have liked him to clearly admit they were wrong.