NATO will celebrate 75 years of collective defense across Europe and North America on April 4 as Russia’s full-scale war on Ukraine enters its third year and sorely tests the allies’ resolve while rising populism gnaws at their unity. U.S. Secretary of State Antony Blinken and his counterparts will mark the moment the alliance’s founding treaty was signed on April 4, 1949, in Washington. Sweden’s foreign minister is taking part in the first ministerial-level meeting since his country became NATO’s 32nd ally last month. The alliance’s ranks have almost tripled over more than seven decades from its 12 founding members.