Ukraine crisis: What's driving Russia's response?
"Russia was against the violent coup [the revolution in Ukraine last month], which was masterminded mostly by the Americans, whose goal is to bring Ukraine into Nato. And that is a red line for Russia," said Vyacheslav Nikonov, a senior member of the Russian parliament.
"Russia regards this as an existential threat and will do whatever it takes to prevent it happening."
Amid the maelstrom of claim and counter-claim surrounding the Ukraine crisis, the words of Mr Nikonov were a rare moment of clarity into the fundamental fears which have been driving Russian policy, ever since it seemed likely the Ukrainian President Viktor Yanukovych would be overthrown by the protest movement in Kiev.
A brief glance at the map of Eastern Europe shows the strategic significance of the huge country that is Ukraine.
From the perspective of the current occupants of the Kremlin, it is one of a string of countries providing a buffer zone between Russia and Europe and in particular the former Eastern Bloc countries which are now members of Nato.
Add to this the fear of losing the navy base in Crimea, which provides access to the Mediterranean for Russia's Black Sea Fleet, and it was almost inevitable Moscow would make a dramatic move.'Bad for everyone'
Russia's much repeated claims that the revolution in Kiev had unleashed hordes of neo-Nazis determined to sweep across eastern Ukraine and drive out its Russian-speaking population is a pretext to cover the real strategic reason for the military intervention in Crimea.
And so far the Kremlin shows no sign of backing down.
Speaking in Sochi on Thursday, President Vladimir Putin again stated that Russia had not started the crisis.
As for the threats from Europe and the United States to impose more sanctions on Russia if it does annexe Crimea following Sunday's referendum, there's an equally blunt response.
"Russia is the fifth largest economy and it has a strong military," says the MP Vyacheslav Nikonov.
"So if there are sanctions, there will be counter sanctions which will be mirror-like.
"We are living in a very united world and I would not really recommend anyone to try to sanction the Russian Federation, because the consequences may be bad not just for Russia but for everyone," he added.Warning to Russians
There is another fear factor driving the Kremlin's seemingly unstoppable campaign to undermine Ukraine's revolution.
It is the worry that a successful revolution on its border would bolster opposition groups in Russia itself, strengthening their belief that mass protests against authoritarian governments can ultimately succeed.
So Moscow's harsh response on the ground in Crimea and its much propagated narrative that revolution leads to chaos and fascism, serve as a warning to the people of Russia themselves.
At the same time, the possibility of soon reclaiming Crimea has the added benefit for the Kremlin of being popular amongst a significant proportion of the Russian population.
Crimea was part of Russia until 1954 when the Soviet leader Nikita Khrushchev decided to hand it back to Ukraine.
"This referendum [in Crimea] is legitimate," says Valerie who lives in Moscow.
"Crimea has always been a Russian land and the fact that one illiterate politician gave it to Ukraine I find illegal. It's all a lie about Russian intervention."
Svetlana, another Muscovite, also believes the people of Crimea have the right to self-determination.
"And I will be happy if they will join Russia," she says.
But on the streets of Moscow there are also plenty of people who are deeply concerned by Russia's intervention in Crimea and the plan to hold a referendum with heavily armed troops there.
"You can't solve the situation with a gun near people's heads'" said one man.
"You can protect Russia's interests through peaceful means as well."