- During the Cold War, NATO effectively defended Western Europe with US nuclear weapons.
- Twelve countries signed the North Atlantic Treaty in 1949, and NATO has since grown to 29 countries, including former Soviet states bordering Russia, which has angered Moscow.
- Here are six occasions, from the building of the Berlin Wall to the September 11 attacks, that NATO faced a crisis.
The North Atlantic Treaty Organization, a pact launched 70 years ago in the ashes of World War II to face Stalin's Soviet threat and bind Western Europe and the US together, is the world's foremost military alliance.
The success of its deterrent power can be seen in a simple reality: NATO's first combat mission only came after the Soviet Union's collapse.
During the Cold War, NATO effectively defended Western Europe with US nuclear weapons, as NATO's office of the historian notes.
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From the treaty signed on April 4, 1949 by 12 powers, NATO has grown to 29 countries and expanded to include former Soviet states on Russia's border, which has angered Moscow.
Its forces now confront Russia, which under President Vladimir Putin seized the Crimean peninsula from Ukraine by force in 2014. The Russian military is developing supposedly unstoppable missiles that travel more than five times the speed of sound and a doomsday torpedo that could irradiate an entire ocean.
This is a look at six times NATO faced a crisis that took it to the brink of war, or into combat.