Finland has become the 31st and latest nation to join NATO after it deposited its instrument of accession to the North Atlantic Treaty with the US government – represented by Secretary of State Antony Blinken – at the alliance’s headquarters in Brussels, Belgium, on April 4.

While Finland has always been a close partner of NATO since the organisation was established on April 4, 1949, the Scandinavian nation set aside years of formal nonalignment to seek protection under the alliance’s umbrella following the Russian invasion of Ukraine’s sovereign territory on February 24, 2022, as well as the growing threat of wider hostilities with Russia across Eastern Europe. The nation formally applied to join the alliance in May 2022, with NATO allies signing Finland’s Accession Protocol on July 5, that year, before all 30 national parliaments voted to ratify the country’s membership – of which, Turkey was the last to accept.

Commenting on the country’s formal ascension into the alliance in a statement on April 4, Finnish President Sauli Niinistö said: “Finland has today become a member of the defence alliance NATO. The era of military nonalignment in our history has come to an end. A new era begins. Each country maximises its own security. So does Finland. At the same time, NATO membership strengthens our international position and room for manoeuvre. As a partner, we have long actively participated in NATO activities. In the future, Finland will make a contribution to NATO’s collective deterrence and defence.”

Despite not being a member of the NATO alliance until now, Finland has been one of the organisation’s closest partner nations and has frequently participated in a plethora of different military exercises led by various member states over the years. The latest example of this cooperation was the participation of Finnish Air Force-operated F/A-18C/D Hornets in the UK-led Exercise Cobra Warrior 23-1, with six examples of the multi-role fighters deploying to RAF Waddington, Lincolnshire, for the event. While NATO Secretary-General Jens Stoltenberg told reporters that no NATO troops would be based in Finland without consent from the nation, he refused to rule out the possibility of more military exercises taking place there.

As Finland shares an 832-mile land border with Russia, its ascension into NATO more than doubles the size of the alliance’s border with the nation, in what is an obvious strategic blow to Russian President Vladimir Putin, who has been long outspoken of NATO’s growing expansion toward Russia. In response to Finland’s ascension to NATO, Dmitry Peskov – a spokesman at the Kremlin – called Finland’s move to join NATO an “encroachment” on Russian security, adding that NATO’s structure was hostile towards Russia.

While Finland’s ascension to NATO is the alliance’s first enlargement since North Macedonia joined the organisation in 2020, it will not be the last. Sweden is expected to be the 32nd nation to join NATO after seeking membership at the same time as Finland. However, Sweden’s ascension to the alliance is still being blocked by Turkey, which has previously accused both Finland and Sweden of housing Kurdish terrorist organisations and, along with Hungary, notably stalled the ascension process for both nations.