NATO remains the cornerstone of Euro-Atlantic security, and the alliance faces its most demanding period since the Cold War. Russia’s war in Ukraine, hybrid attacks on member states, and debates over defense spending and burden-sharing have put the alliance’s core commitments back at the center of strategic debate. This hub explains how the alliance works and where it is under strain: the meaning of Article 4 consultations and the Article 5 collective defense guarantee, the mission of shared assets such as AWACS surveillance aircraft, and NATO deterrence along the eastern flank. The NATO eastern flank, from the Baltic states to Romania, is where allied deterrence is tested most directly, and reinforcing the NATO eastern flank drives much of the alliance’s planning. Fellows and analysts track enlargement, defense spending, and the transatlantic bargain that binds North America to European security. Explore expert analysis and commentary on the alliance’s deterrence, capabilities, and future.