
| 1. Joined 2009. During Bosnian War in 1994, started in NATO program Partnership for Peace. |
| 2. 1949 founding member. Contains NATO headquarters. |
| 3. Joined 2004 along with two other neighbors that were former Soviet Republics. |
| 4. Joined 2023, extending NATO border with Russia by over 800 miles. |
| 5. WW2 Allied power, founding member in 1949. Withdrew in 1966 citing U.S. dominance, rejoined 2009. |
| 6. Part of the country joined in1955, membership reaffirmed after reunification in 1990. |
| 7. Joined 1952, along with a neighboring country that frequently disputes territorial claims in the Aegean. |
| 8. Joined 1999 along with other former Warsaw Pact members on NATO's Eastern flank. |
| 9. Joined 1982. Neutral in WW1 and WW2, traditionally the lowest military spender in the alliance. |
| 10. Joined 2024. Traditionally a non-aligned country but spurred by Russian invasion of Ukraine. |