Finland has joined NATO in a historic shift triggered by the war in Ukraine, prompting anger in Russia where officials have cast the move as a threat. The Finnish flag was raised at the Brussels headquarters of the world’s largest military alliance on Tuesday afternoon, almost a year after Helsinki officially applied to join. Finnish Foreign Minister Pekka Haavisto earlier completed the accession process by handing over an official document to US Secretary of State Antony Blinken; the United States Department of State is the repository of NATO texts concerning membership. Jens Stoltenberg, head of the North Atlantic Treaty Organization (NATO), hailed “a good day for Finland’s security, for Nordic security and for NATO as a whole”. “This will make Finland safer and NATO stronger,” he said. “This has been the fastest accession process in NATO’s history.” Finland President Sauli Väinämö Niinistö said membership was not “targeted against anyone”, adding his country was “stable and predictable”. Finland applied in May, alongside Sweden, as fears of Russian aggression rose in northern Europe following Moscow’s invasion of Ukraine. “Finland’s membership is not complete without Sweden,” said Niinistö. “I look forward to Sweden joining us as the 32nd member.” Neighbouring Sweden, which had avoided military alliances for more than 200 years, is being stalled by objections from NATO members Turkey and Hungary. Finland’s border with Russia stretches across 1,340km (833 miles). Russia has long said NATO enlargement compromises its security and has promised to boost military capacity in its western and northwestern regions, in response to Finland’s membership. Officials in Russia including President Vladimir Putin claim one of the reasons why armed forces were sent into Ukraine in February 2022 was to counter alleged Western plans to use Ukraine as a platform to aggress Russia. They say they are now fighting a “hybrid war” against NATO and the West, which is backing Ukraine with multibillion-dollar packages of arms and financial support. Just before accepting the documents, Blinken said: “I’m tempted to say this is maybe the one thing that we can thank Putin for.” Teivo Teivainen, professor of world politics at the University of Helsinki, told Al Jazeera: “Most people in Finland think that Finland is safe under the protection of the fifth article of NATO.” The idea behind Article 5 is that if one NATO member is attacked, every country in the alliance should take it as an act of aggression. The new membership “is considered to increase the security of Finland”, Teivainen said.