DW 
Finland became the 31st member of the NATO military alliance on Tuesday amid warnings of “countermeasures” from the Kremlin.
Russia’s invasion of Ukraine last year prompted Finland – which has a 1,300-kilometre (800-mile) border with Russia – and its neighbor Sweden to drop decades of military non-alignment.
How is the accession being marked?
Finland’s foreign minister handed the accession papers to US Secretary of State Antony Blinken, the keeper of NATO’s founding treaty.
Finland’s blue and white flag was then set to be hoisted alongside those of its new allies, alphabetically placed between the flags of Estonia and France, in front of NATO headquarters in Brussels.
US top diplomat Antony Blinken took a jab at Russian President Vladimir Putin during the ceremony.
“I’m tempted to say this is maybe the one thing that we can thank Mr. Putin for because he once again here precipitated something he claims to want to prevent by Russia’s aggression, causing many countries to believe that they have to do more to look out for their own defense and to make sure that they can deter possible Russian aggression going forward,” Blinken said, just before accepting the documents that made Finland’s membership official.
NATO secretary-general Jens Stoltenberg echoed the sentiment.
“President Putin wanted to slam NATO’s door shut. Today we show the world that he failed, that aggression and intimidation do not work,” Stoltenberg said.
Finnish security expert Henri Vanhanen told DW that the invasion of Ukraine last year marked a start of a new era.
As soon as Russia attacked “the masks have been removed and we sort of see the real face of Putin right now,” he said. “And I think in the foreseeable future, it will be difficult to see a sort of return to any sort of normal relationship with the Russians, at least as long as the current administration is in place.”
UK wants Sweden to join next
Helsinki will work “relentlessly” to secure Sweden’s membership of NATO, Finnish President Sauli Niinisto pledged after his own country formally joined NATO.
“Finland’s membership is not complete without Swedish membership,” Niinisto said in a statement.
The UK also urged Sweden to join NATO next.
“All NATO members now need to take the steps necessary to admit Sweden too, so we can stand together as one Alliance to defend freedom in Europe and across the world,” the country’s Prime Minister Rishi Sunak said in a statement after Finland officially joined.
Finland’s accession came as NATO foreign ministers met Tuesday at the alliance’s headquarters in Brussels for a two-day summit to discuss the ongoing Russian invasion of Ukraine. The meeting coincides with the 74th anniversary of the alliance’s founding.
Russia’s NATO frontier doubles in length
Russia’s foreign ministry said that, by joining the alliance, Finland had lost “its self-identity and any independence.”
“This forces us to take countermeasures … in tactical and strategic terms,” said Kremlin spokesman Dmitry Peskov.
The enlargement of NATO’s border with Russia has “profoundly changed the situation” in northern Europe, the ministry said. Finland’s membership doubles Russia’s border with NATO, the world’s largest military alliance.
Turkey and Hungary, for different reasons of their own, had held up Finland’s effort to join. Sweden’s progress remains blocked.
Achieving ratification in well under a year still makes Finland’s membership process the fastest in the alliance’s recent history.
Membership for Sweden is still dependent on Turkish ratification due to several sticking points, but NATO Secretary General Jens Stoltenberg pointed out “Sweden will also be safer as a result” of Finland’s membership. He added that he expected Sweden would be able to join soon.
This article was originally published on DW.