Russia is staging its biggest military parade, marking 70 years of victory over Nazi Germany in World War Two.
Thousands of troops are marching on Red Square in Moscow, and new armour has been displayed for the first time.
Many foreign dignitaries are attending, but most Western leaders stayed away because of Russia's role in Ukraine.
President Vladimir Putin said global co-operation had been put at risk in recent years. His Ukrainian counterpart accused him of justifying aggression.