The North Atlantic Treaty Organization (NATO) was created by the North Atlantic Treaty signed in Washington on 4 April 1949, at the start of the Cold War, to counter the Soviet Union (which answered with the Warsaw Pact in 1955). Its heart is Article 5: an armed attack on one member is treated as an attack on all; it has been invoked once, after the 11 September 2001 attacks.
Key facts
- Founded 4 April 1949; 32 members today, 30 in Europe and two in North America. (as of 23 Oct 2026)
- Article 5 collective defence has been invoked only once, after the September 11 attacks.
- Headquarters Brussels; Secretary General Mark Rutte; military HQ (SHAPE) near Mons. (as of 23 Oct 2026)
- Members committed in 2025 to spend 5 percent of GDP on defence by 2035, up from the 2 percent target. (as of 23 Oct 2026)
Why exams ask about it
Founding year and number of founders, newest members, headquarters and Article 5 are standard.