Russia has launched a devastating attack on Ukraine, a European democracy of 44 million people, bombarding its cities and closing in on the capital, Kyiv, prompting a mass exodus of refugees.

But why did Russia's authoritarian leader tear up a peace deal with his neighbour and unleash what European leaders have labelled "Putin's war"?

He has shattered peace in Europe and thrown the continent's entire security structure into jeopardy.

In a pre-dawn TV address on 24 February, President Putin declared Russia could not feel "safe, develop and exist" because of what he claimed was a constant threat from modern Ukraine.

Immediately, airports and military headquarters were attacked, then tanks and troops rolled in from Russia, Russian-annexed Crimea and its ally Belarus. Big cities have been shelled, neighbourhoods razed to the ground and millions of Ukrainians have fled their homes.

And yet Russia bans the terms war or even invasion, threatening journalists with jail if they do. For President Putin this is a "special military operation".

Many of his justifications for war were false or irrational.

He claimed his goal was to protect people subjected to bullying and genocide and aim for the "demilitarisation and de-Nazification" of Ukraine. There has been no genocide in Ukraine: it is a vibrant democracy, led by a president who is Jewish.

"How could I be a Nazi?" said Volodymyr Zelensky, who has likened Russia's onslaught to Nazi Germany's invasion in World War Two. Ukraine's chief rabbi and the Auschwitz Memorial have also rejected Russia's slur.