Since 1945, May 9 is the day on which Russians commemorate their sacrifice and ultimate victory in the Great Patriotic War.
The defeat of Nazi Germany came at a terrible price with more than 27 million dead and most of the European portion of the Soviet Union devastated.
Here's a link to the official Victory Day site. Drop in. It's worth the visit to get a different perspective on the Second World War.
I still remember the shock expressed by many Westerners on the 40th anniversary when legions of vintage T-34/85 tanks in perfect working order rolled down the Moscow streets and into Red Square. They may have been more menacing than this parade of period transport trucks, but the idea is the same. The communists kept anything military and serviceable in storage just in case.
Correction: Earlier I thought Canada was not represented at the Ksocw events. Turns out that Her Excellency the Governor General was the official Canadian representative in Red Square.