Sweden officially joined NATO on Thursday after Russia’s invasion of Ukraine spurred it to rethink its defense policy and abandon its long held position of neutrality, writes CNN.

Swedish Prime Minister Ulf Kristersson formally handed over accession documents to the US State Department in Washington, DC, the final step of a months-long process to gain the approval of all members to allow his country to become the alliance’s 32nd member. US Secretary of State Antony Blinken received the documents, which he said were the product of “nearly two years of tireless diplomacy” by NATO members. The documents are put into a vault at the State Department, which serves as the treaty depositary for NATO.

Sweden joining NATO was scarcely conceivable a little more than two years ago. The country remained neutral in both World Wars but when Russian troops began marching toward Kyiv in February 2022, Sweden – and its Nordic neighbor Finland – became alert to the threat Moscow could pose to nearby countries outside the alliance.