More than 50 world leaders, including US President George W Bush, have paid tribute in Moscow to the Soviet people's sacrifice in World War II.
An estimated 1 million Soviet war veterans are still alive
A mass parade on Red Square was one of the most spectacular events to mark 60 years since the defeat of Nazi Germany.
Wreaths were laid at the Tomb of the Unknown Soldier and veterans remembered the fallen with the traditional wartime toast of "100 grams" of vodka.
Tensions remain over the war's legacy but Monday was a day for commemoration.
Mr Bush put up a united front with Russia's Vladimir Putin on Red Square, the BBC's Sarah Rainsford reports from Moscow.
Their task of the moment, as Mr Putin put it, was to bow in gratitude before those who had fought for their freedom.
Despite the grey skies, Moscow's city centre was transformed into a sea of colour for the celebrations.
They began with four soldiers marching across Red Square with the Soviet victory flag, to the sounds of a military band. Thousands of servicemen in period uniform bearing Red Army standards followed.
World leaders saluted as 2,500 frontline veterans were driven past in open-backed lorries dating from the war, carrying red carnations.
Fighter jets flew over the square streaming red, white and blue smoke, the colours of the Russian flag.
Addressing the selected crowd attending the parade, Mr Putin stressed the extent of the Soviet sacrifice to save the world from the Nazis.
The USSR suffered irreparable losses, losing tens of millions of citizens to the war, he said.
He also paid tribute to the Western powers, saying: "We have never divided the victory between ours and theirs, and we will always remember the help of the allies."
More than 40 million people had lost their lives by the time World War II ended in Europe on 8 May 1945, including 27 million from the Soviet Union.
Old soldiers travelled to Moscow from across Russia and other ex-Soviet states, and the city threw parties for the "frontoviki".
The BBC's Steve Rosenberg found one group in a Moscow park enjoying a wartime sing-song and a picnic - some bread, sausage and a bottle of vodka.
Mr Bush, the first US president to attend a Russian victory parade, had earlier described the post-war Soviet occupation of Eastern Europe as "one of the greatest wrongs of history", while hailing the defeat of the Nazis..
After Tuesday's ceremonies, he travelled on to Georgia - the first US president to visit the former Soviet republic in what analysts see as a clear signal to Moscow.
The ceremonies took place amid tight security and central Moscow was closed off, leading to complaints that the event was not for ordinary people.
World leaders attending included French President Jacques Chirac and Chinese President Hu Jintao.
UK Prime Minister Tony Blair, who is forming a new cabinet following his election victory, did not attend. Britain was represented by Deputy Prime Minister John Prescott.
Japanese Prime Minister Junichiro Koizumi also came, despite the absence of a treaty ending World War II hostilities between Moscow and Tokyo.
Polish President Aleksander Kwasniewski was at the parade, despite strong objections from many Poles who said he should not attend as the defeat of the Nazis in 1945 did not bring freedom to Poland.
The Soviet occupation of the Baltic states prompted Estonia and Lithuania - but not Latvia - to boycott Moscow's commemorations, which mark the signature of the unconditional surrender in Berlin.
Germany's Chancellor Gerhard Schroeder, who was there along with seven veterans from his own country, said "bitter enemies" had become "friends and partners".
A Festival of Democracy is also under way in Germany, in a sign of reconciliation with past enemies and relief at the defeat of the Nazi dictatorship.