BRUSSELS: Finland’s blue-and-white Nordic cross flag was hoisted outside NATO headquarters on Tuesday as it became the 31st member of the alliance, in the first step of a historic realignment of Europe’s defences sparked by Russia’s war on Ukraine.

Western officials will now turn up the pressure on their awkward allies Hungary and Turkey to lift their block on Sweden, so it can also join.

Already Helsinki’s strategic shift — which ended decades of military non-alignment — has doubled the length of the US-led alliance’s land border with Russia and drawn an angry warning of “countermeasures” from the Kremlin.

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Finland’s foreign minister formally sealed Helsinki’s membership by depositing the accession papers before the Finnish flag was raised between those of France and Estonia to the singing of a choir outside NATO’s gleaming Brussels headquarters.

“Finland now has the strongest friends and allies in the world,” NATO chief Jens Stoltenberg said.

Russian President Vladimir Putin, he said, had “wanted to slam NATO’s door shut. Today we show the world that he failed, that aggression and intimidation do not work.”

Joining NATO puts Finland under the alliance’s Article Five, the collective defence pledge that an attack on one member “shall be considered an attack against them all”.

This was the guarantee Finnish leaders decided they needed as they watched Putin’s devastating assault on Uk.