Russian troops launched an attack on Ukraine on 24 February 2022 casting aside the sanctions from the United States and its Western allies.
At the centre of this conflict is the US-led military alliance The North Atlantic Treaty Organisation (NATO).
On 17 December 2021, Russia put forward a list of security guarantees it wanted the West to agree to. The chief of the demands was a ban on Ukraine from becoming a member of NATO. Moscow wanted guarantees that its neighbour, a former Soviet state, would be permanently barred from joining the alliance and also called for NATO to cease all military activity in Eastern Europe.
Blaming NATO for compromising security in the region, Moscow threatened disregarding its concerns that it would lead to a "military response" similar to the Cuban missile crisis of 1962.
They also included a demand that NATO remove any troops or weapons deployed to countries that entered the alliance after 1997, which would include much of eastern Europe, including Poland, the former Soviet countries of Estonia, Lithuania, Latvia and the Balkan countries.
Russia also demanded that NATO rule out further expansion and not hold drills in Ukraine, Eastern Europe, in Caucasus countries such as Georgia or Central Asia without previous agreement from Russia, among other things.
NATO was founded in 1949, in the aftermath of World War II. The alliance was initially part of an effort by the US and its European allies to deter any expansion of the then-Soviet Union (USSR).
In the decades since, it has steadily expanded its orbit, bringing a swathe of central and eastern European states into its ranks after the USSR collapsed.
This enlargement has troubled Moscow, which is wary of the Brussels-headquartered alliance edging ever closer to its borders and skirting it in from the West.
Why Ukraine wants NATO membership
NATO currently comprises 30 member states: Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom and the US were its founding members. Its newest member state is North Macedonia, which joined in 2020.
Three so-called partner countries – Bosnia and Herzegovina, Georgia and most importantly Ukraine – have declared their aspirations to become part of the alliance.
Ukraine has repeatedly stated its intention to become a NATO member state – an objective that is written into the country's constitution.
Joining the alliance would have boosted Ukraine's defensive strength, because of NATO's principle of collective defence, which essentially means an attack against one ally is considered as an attack against all allies, committing them to protect one another.
In 2008, NATO leaders promised Ukraine that it would one day be given the opportunity to join the alliance. But despite deepening cooperation in the years since, the general consensus is, there is little chance of that happening any time soon.
Putin has said it is now time for NATO's waves of expansion to be reversed. He argues that the West has betrayed Moscow by breaking alleged verbal commitments made at the end of the Cold War that NATO would not expand eastwards. The alliance denies that any such promises were made.
A newly discovered document supports his claim. Dated March 1991, it shows that discussions between the West and Russia made it clear that NATO would not expand beyond the Oder River.
In January last year, Ukrainian President Volodymyr Zelenskyy urged US President Joe Biden to let Ukraine join NATO, this incident seemed to have triggered Putin to rehash his plans for Ukraine.