Finland has officially be named the 31st member of NATO, marking a major shift in the security landscape in northeastern Europe that adds some 1,300 kilometers (830 miles) to the alliance’s frontier with Russia.

Finland’s acceptance into the US-led security alliance presents a blow to Russian President Vladimir Putin, who has long sought to undermine NATO, and before invading Ukraine, demanded the bloc refrain from further expansion.

The invasion instead drove non-aligned Finland and Sweden to abandon their neutrality and seek protection within NATO, though Sweden’s attempt to join the bloc has been stalled by alliance members Turkey and Hungary.