The tension along the Ukrainian border had been brewing for months, but escalated in recent months after Russian President Vladimir Putin sent forces to its annexed territory Crimea and neighbouring Belarus. Despite assurances from Moscow that it doesn't plan to attack Kyiv, Western intelligence agencies raised alarm and countries like the United States claimed an attack is imminent.
The Russian forces are stationed just a few kilometres away from the Ukrainian border, along with armoured vehicles, helicopters and heavy weaponry. All this point to Russia's intention of starting a full-scale war in the region, the West has claimed.
Intense diplomatic efforts are on to avoid such a situation, with French President and German Chancellor meeting Putin to convince him to back off. The diplomatic efforts will continue, said US President Joe Biden but has warned of sanctions.
The picture on the ground is changing every day, with Russia releasing videos of troops moving away from the border and US casting doubt over it. Here's what we know about the biggest crisis since Cold War:
The Deployment Of Russian Troops
US intelligence agencies and Ukrainian officials say that Russian troops have surrounded the country from three sides “like a horse shoe”.
Russian-backed separatists packed civilians onto buses out of breakaway regions on Friday. Warning sirens blared in Donetsk after it and the other self-proclaimed region, Luhansk, announced an evacuation to Russia, with women, children and the elderly going first.
Most of the several million civilians in the two rebel-held areas of eastern Ukraine are Russian speakers, with many already granted citizenship by Moscow.
The separatists said that they planned to evacuate around 700,000 people to Russia from Donetsk.
“Most Significant Mobilisation Since World War 2”
With global markets anxious and Europe engulfed in a diplomatic crisis, Russia said this week it had started withdrawing troops from the border near Ukraine.
But the US said it had instead done the opposite: Ramping up the force menacing its neighbour to between 169,000 and 190,000 troops, from 100,000 at the end of January.
Western countries fear a conflict on a scale unseen in Europe at least since the Yugoslav and Chechen wars of the 1990s, which killed hundreds of thousands of people and sent millions to flight.
Ukraine is the second biggest country in Europe by area after Russia, and home to 40 million people.
"This is the most significant military mobilisation in Europe since the Second World War," U.S. ambassador Michael Carpenter told a meeting at the Vienna-based Organization for Security and Cooperation in Europe.
The Military Threat
Russia has assembled troops at Ukrainian border with heavy gear and established new bases, according to Western intelligence agencies. Satellite images released by a private company Maxar Technologies show tanks, armoured vehicles and other military equipment in Crimea and other territories.
The Kremlin also has tens of thousands of troops staging exercises in Belarus, north of Ukraine. At least 20 attack helicopters are part of it, as reported by Maxar. The drills are due to end on Sunday and Moscow has said the troops would go back to Russia at some point after.
How The West Is Tackling The Crisis
US Defence Secretary Lloyd Austin announced on Friday the planned sale of 250 Abrams tanks to Poland, as part of Washington's plan to strengthen the defences of a key eastern European ally amid the threat from Russia. The US has already sent nearly 5,000 additional troops to Poland as well as additional fighter aircraft, in response to the Ukraine crisis.
The Ukraine crisis has prompted the US-led NATO alliance to shore up its presence along its eastern flank in member states, including Lithuania, closer to Russia or Ukraine. Earlier this month, US President Joe Biden said that he will send nearly 3,000 extra troops to Poland and Romania to shield Eastern Europe from a potential spillover from the crisis.
The United Kingdom has sent reinforcements from its 14 battalion to neighbouring countries. Germany too has sent reinforcements to Lithuania to prepare for an impending attack.
The Cause Of The Tension
Russia is making a set of security demands, including a promise to bar Ukraine from ever joining the US-European military alliance NATO, which the West says is any country's sovereign right. On Thursday, Russia sent a strongly-worded letter to Washington threatening unspecified "military-technical measures".
The West has threatened tighter economic sanctions on Russia if it invades Ukraine. Putin, whose nation has already been under sanctions since 2014, told a news conference in Moscow that Western countries would probably find a reason to impose more whatever Russia does anyway.
What Ukrainian Says
Ukraine's President Volodymyr Zelenskiy has ordered an increase in the size of the country's armed forces by 100,000 troops over three years and raise soldiers' salaries, but said it did not mean war with Russia was imminent.
In an address to Parliament earlier this month, he urged lawmakers to stay calm and united, not to sow panic and not to exploit a standoff with Russia for political gain.
Track Latest News Live on NDTV.com and get news updates from India and around the world
