Senior Airman Jeffrey Allen/US Air Force
  • 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 Organisation, 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.

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.

Soviet-backed East Germany built a barbed wire fence through the divided city of Berlin in 1961.

The US positioned tanks of its side of the Berlin checkpoint, facing East German troops, which prompted the Soviets to do the same. Fears ran high that a skirmish between the superpowers could rapidly escalate.

The standoff ended peacefully, but the Berlin Wall would last another 28 years.

Source: US State Department

In October 1962, a US U-2 spy plane snapped photos of Soviet missile sites being built in Cuba.

After days of secret deliberations, President John F. Kennedy imposed a naval blockade around Cuba to block Soviet ships from delivering supplies.

Soviet leader Nikita Khrushchev agreed to withdraw the missiles in return for a US pledge not to invade Cuba, as it had done in the disastrous Bay of Pigs a year before. The US also secretly agreed to remove nuclear missiles stationed in Turkey, a NATO member.

Any conflict between the US and the USSR would likely have involved NATO via the alliance's mutual-defense agreement.

Source: JFK Library

In 1983, a massive NATO exercise nearly triggered a nuclear crisis.

US Air Force

During exercise Able Archer 83, NATO officers practiced preparing for nuclear strikes amid a much larger war game involving 40,000 troops.

The war games seemed to trigger Russian fears that the US and NATO would launch a preemptive nuclear attack to decapitate Soviet leaders, and the USSR placed some of its nuclear force on alert.

Source: The Atlantic

In 1995, NATO launched an air campaign against Bosnian Serbs that brought the war in the Balkan country to an end.

US Army

The Bosnian Serbs, led by Radovan Karadzic, carried out an ethnic-cleansing campaign in Bosnia and Herzegovina designed to wipe out Bosnian Muslims.

The attacks prompted the UN to establish a no-fly zone, which NATO enforced. In February 1994, NATO planes shot down four Serbian jets - the first combat operation in NATO's history.

Serbian forces perpetrated the Srebrenica massacre in July 1995, killing an estimated 8,000 civilians. NATO responded with a bombing campaign that lasted about a month; the Dayton Accords, which brought the Bosnian War to an end, were signed November 1995.

Source: NATO

Another crisis in the Balkans, this time in Kosovo, led to a refugee crisis and mass killings.

NATO, this time without UN Security Council approval, launched a 78-day campaign in 1999 against Serbian forces who were carrying out the majority of the mass killings.

NATO jets flew 38,000 sorties, forcing the Serbs under President Slobodan Milosevic to withdraw their forces from Kosovo.

Serbian forces downed two NATO aircraft during the operation: a US Air Force F-117 stealth aircraft on March 27, 1999, and, on May 2 that year, an F-16 flown by Lt. Col. David Goldfein. Goldfein, now a general, is the current Air Force chief of staff.

NATO peacekeepers are still deployed to Kosovo.

After the September 11, 2001, attacks on the US, NATO invoked its self-defense clause for the first time in its history.

NATO countries formed the International Security Assistance Force to defeat the Taliban in Afghanistan, where Al Qaeda had trained its fighters.

The NATO mission continues as Operation Resolute Support, while the US seeks a negotiated exit from the 17-year war. Two US service members were killed in Afghanistan this month, bringing the total to at least four this year and 65 since January 2015.

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