What is Article 4 of the North Atlantic Treaty? Why do NATO members want it triggered?
Bulgaria, the Czech Republic, Estonia, Latvia, Lithuania, Poland, Romania and Slovakia have urged NATO to hold urgent consultations under Article 4.
The conflict between Ukraine and Russia continues to escalate. Russia president Vladimir Putin has announced a "special military operation to protect people who have been subjected to intimidation and genocide by the Kiev regime for eight years." The current state of affairs is reminiscent of what happened in with the annexation of Crimea in 2014.
Thursday's invasion had been anticipated by the North Atlantic Treaty Organization (NATO) and US intelligence services several few months ago when satellite images confirmed that Russia was amassing troops and weaponry at various points along the border with Ukraine.
Putin does not want Ukraine to join NATO - a move which would be in the interests of the United States. By invading and - the demilitarization of Ukraine, Putin aims to increase his control over the region and position himself as the hegemonic power in an area which, up until August 1991, was part of the Soviet Union.
Latvia, Lithuania and Estonia call to invoke Article 4
Latvia, Lithuania and Estonia are former Soviet republics but today form part of the European Union and NATO.
What does article 4 of the Washington Treaty say?
The North Atlantic Treaty was signed in April 1949 with all signatories committing to "safeguard the freedom, common heritage and civilization of their peoples, founded on the principles of democracy, individual liberty and the rule of law" and pledging "to promote stability and well-being in the North Atlantic area".
Article 4 of the Treaty states:
"The Parties will consult together whenever, in the opinion of any of them, the territorial integrity, political independence or security of any of the Parties is threatened".
Since the Alliance’s creation in 1949, Article 4 has been invoked a total of seven times - four times by Turkey, who requested NATO's assistance for the first time in February 2003 ahead of the Gulf War in Iraq.