A map showing how NATO's current border with Russia compares to its border if Sweden and Finland join.
A map showing how NATO's current border with Russia compares to its border if Sweden and Finland join.
  • Finland officially became a member of the NATO military alliance on Tuesday.

  • Finland has an 830-mile border with Russia, meaning Russia's border with NATO more than doubles.
  • The development is a failure for Russia, which partially justified its Ukraine invasion as a way to stop NATO expansion.

Finland became the latest member of NATO on Tuesday, infuriating Russian President Vladimir Putin who has long aimed at rolling back the military alliance's borders.