Finland officially becomes a member of NATO, doubling the military alliance’s border with Russia

Finland on Tuesday became an official member of the military alliance NATO, 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.

“Finland’s membership is not targeted against anyone. Nor does it change the foundations or objectives of Finland’s foreign and security policy,” Finnish...