Western nations founded NATO in 1949 as a means of collective security against the Soviet Union and its allies. But for more than 70 years, two European countries - Finland and Sweden - declined to join the alliance, instead pursuing careful Cold War policies of neutrality and nonalignment.
After Russia invaded Ukraine last year, both Finland and Sweden abandoned those policies and formally requested to join NATO. Finland is set to join NATO as its 31st member on Tuesday. It's a move that will transform Europe's security landscape and expand Russia's border with NATO. Finland will also gain protection under the alliance's Article 5 collective defense mechanism.