Foreign secretary Liz Truss chaired a meeting of the government’s emergency COBRA committee on the Ukraine crisis on Monday.
Speaking afterwards, she said: “We are fully aware that there could be a Russian invasion almost immediately.”
Truss has since warned that conflict in Ukraine could trigger war around the world.
So what exactly is going on?
How close is a Russian invasion of Ukraine?
Very close... Probably. Boris Johnson said on Monday we are “on the edge of a precipice” but, crucially, it’s not too late for Russian president Vladimir Putin to pull back from the brink.
The presence of 130,000 Russian troops on the Ukrainian border is a pretty clear sign that Moscow wants to go in, despite its protestations to the contrary.
Some Russian troops withdrew on Tuesday – while the Kremlin confusingly declared “the Western propaganda war” had failed – but the West has made it clear all military personnel need to pull back for it to count as de-escalation.
Western countries, including the UK and America, have told their Ukraine-based citizens to leave the country while commercial flights are still available because they will not evacuate them militarily should fighting break out.
The US thinks an invasion could happen within 48 hours, while UK defence minister James Heappey warned that bombing could happen “with no notice”.
Ukraine, meanwhile, thinks that an attack is not imminent, although they seem to be very much in the minority.
Why does Russia want to invade in the first place?
Ukraine declared independence from the Soviet Union in the early-1990s but has maintained close economic and cultural links with Russia.
Kiev’s closer ties with the EU and the overthrow of the country’s last pro-Russian leader, prompted Russia to annexe Crimea, in Ukraine territory, in 2014.
Despite the annexation, Ukraine has been moving ever closer to the west in recent years – something Moscow doesn’t like.
It’s still not entirely clear why Putin is acting right now.
There’s speculation he may be moving because the US looks weak following the messy evacuation from Afghanistan, while soaring oil and gas prices in the EU and the US have provided Russia and its fuel supplies more leverage.
Either way, it’s pretty clear it wants to pull Ukraine away from Nato and the EU.
Why does Russia want to stop Ukraine joining Nato?
Although not a current Nato member, the ambition of joining the Western nuclear alliance is enshrined in the Ukrainian constitution – another reason why Putin is keen to bring the country back under Russian control.
He believes Ukraine and Russia should be under the same sphere of influence, especially as they were key parts of the Soviet Union.
Putin also does not want Ukraine to align itself with all the Western powers which are more sceptical of the Kremlin.
There have been suggestions that war could be avoided if Ukraine were to promise not to pursue Nato membership, although the country is yet to agree to such conditions.
Why does Ukraine want to join Nato?
Unfortunately for the Kremlin, most of Ukraine does want to join Nato and has been determined to do since 2002. The nation is considered a Nato “partner” but support from the group is limited unless it becomes an official member.
Being a member would strengthen both Ukraine’s military – meaning it had more protection against Russian attacks – and its western alliances. It would pave the way for Ukraine to join the EU too, another goal for the country which would enable it to move further away from Russia.
But, for a nation to join, it must contribute to the security of the North Atlantic area and win unanimous approval from current members. Nato also considers “unresolved external territorial disputes” too, which means the Russian troops surrounding Ukraine could pose a threat.
What is the west doing to prevent war?
Intense diplomatic efforts are being made to persuade Russia not to invade.
It has been made clear to Moscow that, should an invasion take place, heavy economic sanctions will immediately be imposed by the west.
Boris Johnson has also warned Putin that any military action will be met with Ukrainian resistance and be “painful, violent and bloody”.
While Ukraine is not a Nato member, members of the alliance have also bolstered their forces in neighbouring nations as a show of force aimed at dissuading Russia from invading.
Why does it matter to the UK what happens in Ukraine?
In the middle of a global energy crisis, a war involving Russia is the last thing the world needs.
Europe gets about 40% of its gas imports from Russia, meaning military tensions could have a significant impact on Britain’s already struggling energy supply. It would most likely send wholesale gas prices soaring even further, which would be felt lead to higher bills for British families.
With this in mind, Johnson said Europe must cut its reliance on Russian energy.
“Yank out that hypodermic drip feed of Russian hydrocarbons that is keeping so many European economies going,” he said.
“We need to find alternative sources of energy and we need to get ready to impose some very, very severe economic consequences on Russia.”
The UK, the US and the EU are all unavoidably involved in the crisis through membership of Nato, and any Russian military action would be a huge test of the west’s resolve and its willingness to defend a nascent democracy on the eastern edge of Europe.
So what happens next?
As we wait for Russia to make its next move, diplomatic efforts to avoid war are being re-doubled.
Defence Secretary Ben Wallace announced on Sunday that he was cancelling a family holiday to concentrate on the crisis, while Johnson is continuing talks with world leaders and is expected to travel to Europe later this week for further talks.
And all the while, the world holds its breath.