For the first time ever, NATO will deploy its rapid response force for the first time ever to bolster its eastern flank.

In this "historic" deployment, the 40,000-strong response force will be ready year-round and will be able to respond within two or three days when a security crisis emerges.

NATO agreed to activate the force on Thursday; however, it will not be deployed to Ukraine, as it is not a member of the alliance.

The Northern Atlantic Alliance Organization's overall command is currently headed by the Supreme Allied Commander Europe, US General Tod D. Wolters, who called the force's activation a "historic moment".

Following Russia's 2014 annexation of Crimea, a special "spearhead" force was added to it, and is NATO's "highest-readiness element."

The Very High Readiness Joint Task Force is a 20,000 strong force, whose leadership rotates annually. It is currently held by France and will be followed by Germany in 2023. 

NATO's Secretary-General Jens Stoltenberg did not provide details on Friday on where the forces were being sent.

NATO Article 4

Estonia's Prime Minister had declared on Thursday that her government decided to trigger NATO consultations under the Alliance's Article 4 in cooperation with Latvia, Lithuania, and Poland, citing a "threat to the entire free world" posed by Russia's military operation in Donbass.

According to Article 4 of NATO's founding treaty, members consult together when in the opinion of any of them "the territorial integrity, political independence or security of any of the Parties is threatened."

As soon as Article 4 is invoked, the issue is discussed and can lead to some form of joint decision or action in the alliance. The article has been invoked six times since NATO's creation in 1949.

Russia has for months been warning of the threat posed against it by NATO's attempts to expand eastward, which happened alongside an increase in NATO military activity along Russia's borders, and batches of lethal weapons being sent to Ukraine, prompting Russia to request security guarantees from the West. Washington failed to provide the guarantees.

“They [Ukraine] vowed not to advance NATO, they didn’t keep their promise, they say: 'We didn’t sign anything.' But we know when and to whom such promises, such assurances were given. Did they promise not to advance, for example, to the territory of the former Soviet Union? They promised it in private conversations. They did not fulfill the promise. And now they are already moving right onto our borders," Deputy Chairman of the Russian Security Council, Dmitry Medvedev said on January 27.