Russia has deployed tens of thousands of troops near the Ukraine border, triggering the worst security crisis to emerge between Moscow and the West since the Cold War.
The West, led by the US, has thrown its weight behind Ukraine, which lost control of its Crimean Peninsula when Russia annexed it in 2014.
The Kremlin has justified its military muscle-flexing as an attempt to counter decades of NATO expansion in the region. Russia has demanded legally binding guarantees that the NATO alliance will not embrace Ukraine and other former Soviet nations, or place weapons there. It also wants NATO to pull back its forces from countries in Central and Eastern Europe that joined the alliance since the 1990s.
Russia has also been accused of backing armed separatists in eastern Ukraine. The conflict has left more than 13,000 people dead in nearly eight years of fighting. A 2015 peace deal brokered by France and Germany helped end large-scale battles, but a political settlement has stalled, and frequent skirmishes have continued along the tense line of contact.
In early 2021, a spike in ceasefire violations in the east and a Russian troop concentration near Ukraine ignited the invasion fears, but tensions abated when Moscow pulled back the bulk of its forces after manoeuvres in April.
The military buildup near Ukraine resumed in late 2021, with Ukrainian and Western officials warning that the increased troop concentration could herald a multipronged Russian attack.