Why does Russia celebrate Victory Day on May 9, and what does it mean for Putin?

(Reuters) -Here's a quick briefing on what Russia is commemorating on Tuesday and why it matters for President Vladimir Putin.

WHAT IS SPECIAL ABOUT THE DATE OF MAY 9?

For Russians, Tuesday marks the 78th anniversary of victory over Nazi Germany in World War Two. The Soviet Union - then including not only Russia but also Ukraine, Belarus and others - lost 27 million people in what Russians call the "Great Patriotic War", more than any other country.

WHY DOES IT MATTER RIGHT NOW?

Victory Day is one of Russia's most important public holidays. For Putin, it is an opportunity to project to his people an image of Russia as a powerful nation of winners, standing on the right side of history in defeating fascism.

He has repeatedly likened the war in Ukraine, where his forces launched a full-scale invasion in February last year, to the challenge of fighting Adolf Hitler. Ukraine and its Western allies denounce that as a false narrative to justify the seizure of Ukrainian land, the destruction of cities, the deaths of tens of thousands of people and the creation of millions of refugees.

Ukrainian President Volodymyr Zelenskiy said on Monday that it was modern Russia that was now pursuing the Nazis' goal of "enslavement and destruction".

WHEN WAS THE FIRST VICTORY DAY?

Nazi Germany's unconditional surrender came into force at 11:01 p.m. on May 8, 1945, marked as "Victory in Europe Day" by France, Britain and the United States. In Moscow it was already May 9, which became the Soviet Union's "Victory Day".

Soviet leader Josef Stalin decreed a holiday, and the first victory parade on Red Square, featuring captured German insignia, was held on June 24, 1945.

HOW DID VICTORY DAY EVOLVE OVER THE YEARS?

The Soviet Union celebrated the 20th and 40th anniversaries of Victory Day with Red Square parades in 1965 and 1985. After the fall of the Soviet Union, Russian President Boris Yeltsin made them an annual event from 1995.

Under Putin, Victory Day increasingly became a muscular display not only of marching battalions but also of Russia's latest weaponry, including warplanes, tanks, and nuclear-capable intercontinental ballistic missiles.

WHAT WAS SPECIAL ABOUT THE BUILD-UP THIS YEAR?

In the two weeks leading up to this year's event, Russia saw a sharp increase in attacks on its own territory, including on freight trains and a major oil refinery. A well-known nationalist writer was wounded when his car was blown up by a bomb last weekend.

Most dramatically of all, Russia accused Ukraine and the West of an attempted drone attack on the Kremlin citadel itself on May 3, specifically linking the incident to the May 9 build-up. Ukraine denied it, and the United States said Russian accusations that it orchestrated the alleged attack were "lies".

All these events combined have forced Russia to bolster security and scale back celebrations across the country, underscoring the fact that its "special military operation" in Ukraine is not proceeding according to Putin's script.

WHAT DID PUTIN SAY THIS TIME?

Putin said Russia was in a "sacred" fight with the West over Ukraine. He accused the West of being consumed by Russophobia, and of forgetting the decisive role of the Soviet Union in defeating Hitler.

But beyond these messages - familiar from many previous Putin speeches - he said nothing new about the state of the war or the strategy to achieve victory.

Putin spoke for only 10 minutes, a minute less than last year. He watched as thousands of soldiers then marched across Red Square to the accompaniment of stirring martial music, but the accompanying parade of military hardware was drastically pared back by comparison with previous years. The entire event on the square was over in well under an hour.

(Writing by Mark TrevelyanEditing by Gareth Jones)