Finland joins NATO in historic shift, Russia threatens 'counter-measures'

Finnish Foreign Minister Pekka Haavisto shakes hands with U.S. Secretary of State Antony Blinken as NATO Secretary-General Jens Stoltenberg stands during a joining ceremony at the NATO foreign ministers' meeting at the Alliance's headquarters in Brussels, Belgium April 4, 2023. REUTERS/Johanna Geron/Pool

HELSINKI/BRUSSELS (Reuters) - Finland formally joined NATO on Tuesday, its flag unfurling outside the military bloc's Brussels headquarters, in a historic policy shift brought on by Russia's invasion of Ukraine that drew a threat from Moscow of "counter-measures."

Finland's accession, ending seven decades of military non-alignment, roughly doubles the length of the border the North Atlantic Treaty Organization shares with Russia and bolsters its eastern flank as the war in Ukraine grinds on with no resolution in sight.