In a moment of huge symbolism, soldiers from Britain, France, Poland and the United States paraded on the square's famous cobbles in Moscow at the same time as nuclear-capable missiles that once would have been aimed at Western states.
Britain and the United States were the key allies of the Soviet Union in World War II but became bitter foes postwar. France and Poland were occupied by the Nazis but their exiled troops played a major role in the Allied effort.
"Sixty-five years ago, Nazism was defeated and a machine that was exterminating whole peoples was halted," President Dmitry Medvedev said in a speech to the parade.
"There was blood and tears. There was one choice -- either victory or to become slaves. The war made us a strong nation."
Two dozen world leaders attended the parade for the 65th anniversary of the victory, including Chinese President Hu Jintao, German Chancellor Angela Merkel and the heads of state of almost all the ex-Soviet nations.
Under blazing sunshine and to the sound of thunderous military music, Britain's 1st Battalion Welsh Guards marched in their full ceremonial uniform including traditional bearskin hats, red jackets and black trousers.
France was represented by the Normandie-Niemen squadron, which fought on the Eastern Front, the United States by a detachment from the 2nd Battalion, 18th Regiment, and Poland by a ceremonial guard of honour.
Minutes later, hundreds of Russian tanks and missile systems rolled through the square past the VIP grandstand erected in front of Lenin's mausoleum, on which Joseph Stalin stood to welcome Soviet troops home in 1945.
Regiments also marched from almost all the ex-Soviet states, with the detachment from Turkmenistan led by a commander on a white stallion, the great-grandson of the steed ridden by Marshal Georgy Zhukov in the 1945 parade.
The parade culminated with the entrance of three nuclear-capable Topol-M missiles, which have a range of 11,000 kilometres (7,000 miles).
A procession of 127 military aircraft roared through the sky, some leaving blue, red and white plumes of smoke in the colours of the Russian flag and others flying in formation to spell out the number 65.
Other planes included a special Ilyushin Il-80 designed to accommodate the Russian leadership in case of a nuclear attack.
Over 10,000 Russian troops took part in the finely choreographed parade which appeared aimed at impressing the world with Russia's post-Soviet resurgence.
"Greetings, comrades! I congratulate you on the 65th anniversary of victory in the Great Patriotic War," declai...