KEY POINTS
  • Authorities in Helsinki decided that in the wake of Russia's full-scale invasion of Ukraine in February 2022, the country was no longer safe on its own and applied to join the alliance a few months later.
  • Finland shares an 832-mile border with Russia, the longest of any European Union member.
  • NATO's border with Russia will roughly double in size after Finland's accession.
Finnish Foreign Affairs Minister Pekka Haavisto (L) shakes hands with US Secretary of State Antony Blinken, flanked by NATO Secretary-General Jens Stoltenberg (C) as he hands over Finland's accession to NATO documents,

Finland on Tuesday became an official member of the NATO military alliance, prompted by Russian President Vladimir Putin's decision to invade Ukraine last year.

The Nordic nation is the 31st country to join the alliance, which vows in its treaty that an attack on one of its members is an attack on them all. It's a historic moment for Finland, which has followed a path of neutrality for decades.