Why has Russia invaded Ukraine and what does Putin want?

Vladimir Putin unleashed the biggest war in Europe since World War Two with the justification that modern, Western-leaning Ukraine was a constant threat and Russia could not feel "safe, develop and exist".

Thousands of people have since died, towns and cities such as Mariupol lie in ruins and 13 million people have been displaced. But the questions remain: what was it all for and how will it end?

            What was Putin's original goal?

The Russian leader's initial aim was to overrun Ukraine and depose its government, ending for good its desire to join the Western defensive alliance Nato. After a month of failures, he abandoned his bid to capture the capital Kyiv and turned his ambitions to Ukraine's east and south.

Launching the invasion on 24 February he told the Russian people his goal was to "demilitarise and de-Nazify Ukraine". His declared aim was to protect people subjected to what he called eight years of bullying and genocide by Ukraine's government. Another objective was soon added: ensuring Ukraine's neutral status .

Foreign Minister Sergei Lavrov spoke of freeing Ukraine from oppression while foreign intelligence chief Sergei Naryshkin argued "Russia's future and its future place in the world are at stake".

Ukraine's democratically elected president, Volodymyr Zelensky, said "the enemy has designated me as target number one; my family is target number two". His adviser said Russian troops made two attempts to storm the presidential compound.

Russia's leader refused to call it an invasion or a war. Moscow continues to coin Europe's biggest war since 1945 a "special military operation".

The claims of Nazis and genocide in Ukraine are completely unfounded but part of a narrative repeated by Russia for years. "It's crazy, sometimes not even they can explain what they are referring to," complained Ukraine's foreign minister Dmytro Kuleba.

However, an opinion piece by state-run news agency Ria Novosti made clear that "denazification is inevitably also de-Ukrainisation" - in effect erasing the modern state.

And it is Russia that is now accused by the international community of carrying out war crimes. Several countries including the US and Canada go further and call it genocide.

After so much destruction, the Russian leader's words ring very hollow now: "It is not our plan to occupy the Ukrainian territory; we do not intend to impose anything on anyone by force."

How have Putin's aims changed?

A month into the invasion, Russia pulled back from Kyiv and declared its main goal was the "liberation of Donbas" - broadly referring to Ukraine's eastern regions of Luhansk and Donetsk. More than a third of this area was already seized by Russian proxy forces in a war that began in 2014, now Russia wanted to conquer all of it.

The Kremlin claimed it had "generally accomplished" the aims of the invasion's first phase, which it defined as considerably reducing Ukraine's combat potential. But it became clear from Russia's withdrawal that it had scaled back its ambitions.

"Putin needs a victory," said Andrei Kortunov, head of the Russian International Affairs Council. "At least he needs something he can present to his constituency at home as a victory."

Russian officials are now focused on seizing the two big eastern regions and creating a land corridor along the south coast, east from Crimea to the Russian border. They have claimed control of the southern region of Kherson and a leading Russian general has said they have hopes of seizing territory further west along the Black Sea coast towards Odesa and beyond.

"Control over the south of Ukraine is another way out to Transnistria," said Maj Gen Rustam Minnekayev, referring to a breakaway area of Moldova, where Russia has some 1,500 troops.

Is there a way out?

There is little sign of any negotiated end to this war in the immediate future.

A few weeks into the war, Russia said it was considering a Ukrainian proposal of neutrality, but there have been no negotiations since the end of March.

President Putin told the UN Secretary General at the end of April "we are negotiating, we do not reject [talks]", but he earlier declared negotiations at a dead end. After a meeting with the Russian leader, Austrian Chancellor Karl Nehammer gave a very downbeat assessment of a man who had entered into a "logic of war".

Ukraine's Volodymyr Zelensky had already accepted that Ukraine would not join Nato: "It's a truth and it must be recognised." But after apparent Russian atrocities came to light in Bucha, Mariupol and elsewhere, he made it clear there would be no more talks until Russia withdrew from all territories seized since 24 February.

In its offer of neutrality proposed at the end of March, Kyiv said:

• Ukraine would become a non-aligned and "non-nuclear" state, with no foreign military bases or contingents on its territory
• Strict, legally binding guarantees would require other countries to protect a neutral Ukraine in the event of attack
• Within three days guarantor states would have to hold consultations and come to Ukraine's defence
• Ukraine would be allowed to join the European Union, but would not enter military-political alliances and any international exercises would require consent of guarantor states
• The future status of Russian-annexed Crimea would be negotiated over the next 15 years

But neutrality for Vladimir Putin was never likely to be enough.

"Ultimately [Putin] wanted to divide the country and I think it's becoming more evident that's what he wants," says Barbara Zanchetta of King's College London's Department of War Studies.

While the Kremlin wants to annex some areas of Ukraine, Tatiana Stanovaya believes "much more important is the fate of Ukraine: Putin wants to end Ukraine as a current state".

How Putin sees Ukraine

Since Ukraine achieved independence in 1991, as the Soviet Union collapsed, it has gradually looked to the West - both the EU and Nato.

Russia's leader has sought to reverse that, seeing the fall of the Soviet Union as the "disintegration of historical Russia". He has claimed Russians and Ukrainians are one people, denying Ukraine its long history and seeing today's independent state merely as an "anti-Russia project". "Ukraine never had stable traditions of genuine statehood," he asserted.

It was his pressure on Ukraine's pro-Russian leader, Viktor Yanukovych, not to sign a deal with the European Union in 2013 that led to protests that ultimately ousted the Ukrainian president in February 2014.

Russia then seized Ukraine's southern region of Crimea and triggered a separatist rebellion in the east and a war that claimed 14,000 lives.

As he prepared to invade in February, he tore up an unfulfilled 2015 Minsk peace deal and accused Nato of threatening "our historic future as a nation", claiming without foundation that Nato countries wanted to bring war to Crimea. He has lately accused Nato of using Ukraine to wage a proxy war against Russia.