CNN  —  Finland officially became the 31st member of the North Atlantic Treaty Organization (NATO) on Tuesday, 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. The Nordic nation’s accession was sealed during a formal ceremony at the NATO headquarters in Brussels on Tuesday. US Secretary of State Antony Blinken and NATO Secretary General Jens Stoltenberg were on hand as the Minister for Foreign Affairs, Pekka Haavisto, established Finland’s accession. “Finland has today become a member of the defense alliance NATO. The era of military non-alignment in our history has come to an end. A…