Russian president Vladimir Putin is playing mind games with the rest of the world over a potential war with Ukraine, a leading expert from The Australian National University (ANU) says.
But, it's just one of a number of factors in a minefield of scenarios that could spark major conflict.
What is triggering a potential war between Ukraine and Russia?
The threat of war in the European hotspot is nothing new, according to Research Fellow at the ANU Centre for European Studies Dr Sonia Mycak, who says more than 15,000 Ukrainian soldiers and civilians have already been killed in a war started by Russia eight years ago.
"It is easy to see the amassing of Russian troops and weaponry along the border with Ukraine as a recent act of aggression," Mycak says.
"However, Ukraine has been in a war started by Russia for eight years, ever since Russian forces occupied Crimea and invaded eastern Ukraine."
Emeritus Professor Paul Dibb from the ANU Strategic and Defence Studies Centre says the mindset of Russian president Vladimir Putin is also a key trigger point.
"We need to begin by recalling what happened to the Soviet Union as it collapsed in 1991 and how this calamity continues to dominate thinking in the Kremlin," Dibb says.
"Putin recalls the Soviet collapse as a time when gross injustice was done to the Russian people. It was only when the Crimea ended up as part of a different country that Russia realised that it had not simply been robbed but plundered."
The collapse of the four-century-old Russian empire and Russia's position as a great power has also been at the forefront of political leaders, especially US presidents.
"Many in Washington wanted to break up the Soviet Union for security reasons," Dibb says.
"The US Secretary of the Treasury, Nicholas Brady, advised President George HW Bush that America's strategic priority was to see the Soviets become 'a third-rate power'."
Mycak says Putin has never accepted the disintegration of the Soviet Union.
"Putin has imperialistic ambitions to take control of Ukrainian territory and re-establish a Russian Empire. Such ambitions date back hundreds of years to the Tsarist regime and later to the USSR," she says.
"Russia cannot accept the existence of an independent Ukraine. Russian ideology does not recognise that Ukrainians are a separate people with their own distinct language, culture and identity. This ideology lies at the base of Putin's actions."
Others have described Putin less admirably, saying he is all about revenge and power.
In his memoir, former US president Barack Obama said Putin resembled the old style corrupt American political bosses who ran US cities.
Why is Ukraine crucial to Russia?
Putin believes the US has conspired to break up his country and encourage the creation of a separate country called Ukraine.
Visiting Professor at the ANU Strategic and Defence Studies Centre Clive Williams says Russia is very concerned about the expansion of the North Atlantic Treaty Organisation (NATO) and particularly about Ukraine becoming part of NATO.
"President Putin faces the problem that if he fails to stop Ukraine from joining NATO," Williams says.
"He and Russia will be seen as weak, and that will encourage others, like China, to be more assertive in their territorial disputes with Russia. It might also encourage other former members of the Soviet bloc to join NATO."
Dibb agrees, pointing to Putin's belief that Soviet leader Mikhail Gorbachev's fumbling policies of reform generated total chaos that legitimised runaway separatism in the Baltics and, ultimately, in the core Slavic territories of Russia, Ukraine and Belarus.
"Putin now proclaims Ukraine's membership of NATO is a 'red-line' issue for Moscow and that he wants written guarantees from the US that Ukraine NATO membership will never be allowed," he says.
Mycak contends that Ukraine, being a sovereign state and independent nation, should have the right to enter into international agreements and develop its own political ambitions, such as joining the European Union or NATO.
What are the implications for Australia and the rest of the world?
If a war were to start, Russia could face sanctions by Western nations.
There could also be an impact on global fuel prices, given that oil and gas pipelines flow to Europe from Russia.
Mycak says the repercussions for Europe will be massive if Putin is allowed to further invade Ukraine.
"Economists agree the global economy would be impacted through the effect on financial markets, commodity production, metal resources and manufacturing, and oil and gas supply," she says.
"Such quantifiable consequences aside, Putin's actions are shaking the foundations of the modern world. Our contemporary world should not be one in which a large and aggressive neighbour can appropriate territory at any time through brute force."
How soon could a war start?
Professor Dibb quotes US Secretary of State Antony Blinken, who said this week: "We're in a window when an invasion could begin at any time and, to be clear, that includes during the Olympics".
Australia and other countries have removed their staff from embassies in Russia and Ukraine which is a clear sign of a potential war, however, media reports have Putin saying he has withdrawn some troops from Ukraine borders.
But there are still about 130,000 troops amassed at the border between Ukraine and Russia. Meanwhile, the world is still holding its breath over when or if Putin will take the first shot.
