Ukrainian President Volodymyr Zelensky, a comedian who had no experience of politics when elected less than three years ago, has suddenly emerged as a convincing war leader.

He has rallied the nation with his addresses and video selfies and given voice to Ukrainian anger and defiance of Russian aggression.

While Russian President Vladimir Putin has appeared increasingly erratic - accusing Ukraine of "genocide" in the breakaway Donetsk and Luhansk republics, and talking of the need to "de-Nazify" the country - President Zelensky, from a Russian-speaking Jewish family, has remained dignified, resolute and articulate.

These pronouncements have revealed a side that many critics - including a large chunk of the intelligentsia - had not seen coming.

A key moment in the transformation from a leader floundering in the polls, who sometimes appeared out of his depth, into a national figurehead came in the early hours of Thursday, a few hours before Russia's invasion. In a sober address posted on social media, speaking partly in Russian, he said he had tried to call Vladimir Putin to avert a war and had been met by silence.

The two countries didn't need a war, "not a Cold War, not a hot war, not a hybrid war", he said, wearing a dark suit as he stood in front of a map of Ukraine. But he added that if Ukrainians came under attack they would defend themselves. "When you attack us you will see our faces - not our backs, but our faces."

Soon afterwards the invasion began, and for his next broadcast, in the middle of the day, he wore military fatigues, reflecting the country's David-versus-Goliath struggle. That evening he made another address, warning Western leaders that if they did not provide assistance then tomorrow "war will knock on your doors".

"This is the sound of a new iron curtain, which has come down, and is cutting Russia off from the civilised world."

Zelensky as commander-in-chief appeared to strike all the right notes on Ukrainian Twitter.

Yulia McGuffie, editor-in-chief of the Novoye Vremya news website, says she was upset when he was elected president in April 2019, as she had no faith in his ability to lead a government.

But Ukrainians have rapidly warmed to their president in the past week, she says.

"Full support and respect came, I think after Russia started its war - all Ukrainians have closed ranks around Zelensky. He is playing a uniting and I would say inspiring role, partly by his own example. He is leading a government that is repelling Putin's army, and for that many sincerely admire and respect him."

Zelensky's arrival on the political scene was a case of life imitating art. His most celebrated role as a comic actor was in the TV series, Servant of the People, in which he played a school teacher catapulted into the presidency after a student posted a viral video of him ranting about corruption in politics.

His candidacy in the 2019 presidential election was initially seen by some as a joke - his political party is called the Servant of the People party. But he went on to win with 73% of the vote, promising to fight corruption and bring peace in the east of the country.

The Ukrainian president has significant powers, but delivering on these promises was always going to be tough, communications consultant Yaryna Klyuchkovska notes. And for someone starting a presidency with such a high approval rating, the only way was down.

"It's one thing to make such broad-ranging promises and another thing to execute these policies," she says.

Years before politics

• Born in the central city of Kryvyi Rih, east Ukraine, in 1978
• Graduated from Kyiv National Economic University with a law degree
• Co-founded a successful TV production company
• Produced shows for a network owned by controversial billionaire Ihor Kolomoisky
• Kolomoisky later backed his presidential bid
• Until the mid-2010s, his career in TV and films was his main focus

Zelensky had enjoyed the support of oligarch Ihor Kolomoisky during his presidential campaign, leading many to fear he would turn out to be a puppet leader, controlled by a man who is under investigation in the US for possible fraud and money-laundering.

He had in fact proved to be more independent than the sceptics thought, refusing for example to allow the re-privatisation of PrivatBank, which was owned by Kolomoisky before it was nationalised.

On the other hand corruption remains deep-rooted in Ukraine, and there are concerns that a new anti-oligarch law could be used to restrict the activities of some oligarchs and not others. Corruption charges aimed at Zelensky's main rival, Petro Poroshenko, his predecessor as president, are regarded by some Western officials as politically motivated.

Zelensky's attempts to negotiate with Russia in order to find a solution to the conflict in the east, which has left more than 14,000 people dead, also had only limited success. There were prisoner exchanges and moves towards implementing parts of a peace process, known as the Minsk agreements, but no breakthrough. Throughout 2020 his approval rating steadily fell.

Zelensky subsequently struck a more assertive tone in pushing for membership of the European Union and the Nato military alliance, a move that was bound to anger the Russian president.

But Yaryna Klyuchkovska says Zelensky's rhetoric on the conflict in the east and relations with Russia continued to be too timid for many Ukrainians, until recent days.

As the drumbeat of war grew louder he declared a Day of Peace, and continued to emphasise his hopes for a diplomatic situation even while Ukraine was reporting a rapid increase in ceasefire violations along the front line.

"He avoided the subject of war, warfare, anything military. It was a topic outside his comfort zone and he was not willing to go there in his public rhetoric," Klyuchkovska says.

He also took issue with the daily warnings from the US and other Western governments of an imminent Russian attack, saying that the US communication strategy was "very expensive for Ukraine".

The big change of tack came with a speech he made to the Munich Security Conference on Saturday 19 February, Klyuchkovska says, converting her too from a sceptic to a fan. He began by describing a visit to a kindergarten in the east of the country that had days earlier been hit by a missile.

"When a bomb crater appears in a school playground, children have a question: 'Has the world forgotten the mistakes of the 20th Century?'" he said.

"Indifference makes you an accomplice," he told the guests from the West's diplomatic and defence elites. He reminded them of Vladimir Putin's rejection of a US-led world order at the same conference exactly 15 years earlier, and his assertion of Russia's resurgence. "How did the world respond? With appeasement."

Klyuchkovska says no Ukrainian leader had spoken so bluntly to the West before.

"For me the moment of pride in Zelensky came during his brilliant speech at the security conference in Munich," says Yulia McGuffie. "It was then that many of Zelensky's political opponents in Ukraine decided that now is not the time for rows and conflicts."

Western intelligence claims that Zelensky's name is the first on a list of people Russian forces aim to kill. He says his family is second on the list, but that he and they remain in Ukraine.

His presence is confirmed by the video selfies he has been shooting outside the presidential administration and the very distinctive House of Chimeras opposite it, adorned with representations of exotic animals and hunting scenes.

In response to one of these, British writer Ben Judah tweeted: "If you'd told many of our great-grandparents in the Pale [the area of the Russian empire in which Jews were mostly confined] that a Jewish man would be a Ukrainian war leader against a Russian invasion they would have blinked incredulously."

"Of course, he is an actor. I don't know whether it's his true persona or not. But whatever he's doing, it's working," says Yaryna Klyuchkovska. "His speech writers have found their stride. They come from the entertainment business, but even writing a Netflix show is different from writing presidential speeches."

Ukraine still faces overwhelming odds. Russia's invasion force is huge and well-armed. But the 44-year-old law graduate, a political newbie, has found a voice that has helped to bolster Ukrainian morale.

"One of my good friends has just written, 'Zelensky has suddenly grown cojones of cosmic proportions'," says McGuffie. "And this really reflects the attitude to him right now."

Additional reporting by Kateryna Khinkulova.