Leading article: Russia must one day confess its part in Poland's misfortune

Seventy years ago today, Adolf Hitler's armies streamed across the western border of Poland, plunging Europe into that six-year-long cataclysm known as the Second World War.

These years would see the virtual extermination of European Jewry in concentration camps, the names of which have passed into history as places of almost unimaginable suffering. Indeed, the scale of Jewish martyrdom in the war has no equal, for almost 80 per cent of the 7 million Jews living in Europe had perished by 1945.

But of the actual states caught in the war, none suffered as terribly as Poland – its territory was overrun and partitioned, its people enslaved and its capital reduced to rubble. A bitter anniversary for Poland, therefore. And an uncomfortable one for one of the leaders of the former Allied powers descending on Gdansk for the anniversary, because, of course, Poland was attacked from the east as well as the west; Nazi Germany and Soviet Russia agreed to divide the Polish spoils between them in August 1939 under the Ribbentrop-Molotov pact.

Poles remember the Russian attack, which was carried out in co-ordination with the terms of the pact, with almost as much bitterness as the German invasion. It was, after all, the Soviets and not the Germans who carried out the mass execution of thousands of Polish officers in the forest of Katyn, only to brazenly deny this atrocity for decades.

To the anger of the Poles, as well as the other victims of the Nazi-Soviet pact, Russia has never really admitted its hand in the bloody carve-up of Eastern Europe, except in weasel words. That is why many eyes will be trained on the Russian Prime Minister Vladimir Putin's demeanour today in Gdansk. Nervous of prompting a hostile public reaction from his Polish hosts, he delivered some conciliatory words just before leaving Moscow. But they were still disappointingly opaque and evasive, professing understanding for Poland's sense of hurt while still defending the Nazi-Soviet pact as laudable.

Underneath this display of bravado, Russia's leaders surely feel, if not shame, then some embarrassment about their hand in Poland's destruction. It is why they refuse to acknowledge 1 September as a date of any great significance, let alone mark it as the anniversary of the war's beginning. That date is, simply, uncomfortably close to 23 August 1939, when Messrs Molotov and Ribbentrop signed their infamous pact. Indeed, the Russians were initially inclined not to attend today's Gdansk ceremony at all, until it became clear that their absence would only draw attention to a discussion about their former role in Poland's catastrophe.

It is good that Prime Minister Putin has changed his mind and is joining the other world leaders, including Israel's Prime Minister, Benjamin Netanyahu, in Gdansk. After all, no one denies that the war could not have been won without Russia, or disputes the scale of Russian suffering after Hitler double-crossed his ally in the Kremlin.

The real pity is that the Kremlin's modern occupants still attempt to glorify Stalin's monstrous aggression towards his neighbours in 1939 at the same time as – rightly – praising the subsequent wartime valour and heroism of the ordinary people of what was then the USSR. Presumably, Russia will one day come to terms with this dark page in its national history. But to judge from Mr Putin's words so far, 70 years on, we are not there yet.