What are the most powerful armies in NATO?
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(CNN) --
NATO, the North Atlantic Treaty Organization, its full name, is a non-aggressive European and North American defense alliance created to promote peace and stability and safeguard the security of its members.
The organization, which is based in Brussels, Belgium, was created as the Cold War escalated.
Its objective was to protect the countries of Western Europe from the threat posed by the Soviet Union and to counter the spread of communism after World War II.
In April 1949, its 12 founders—the United States, Canada, the United Kingdom, France, and eight other European nations—signed the North Atlantic Treaty, pledging to protect each other by political and military means.
Since then, the alliance has grown: today it has 30 members.
In alphabetical order, they are: Albania, Germany, Belgium, Bulgaria, Canada, Croatia, Denmark, Slovakia, Slovenia, Spain, United States, Estonia, France, Greece, Hungary, Iceland, Italy, Latvia, Lithuania, Luxembourg, North Macedonia , Montenegro, Norway, the Netherlands, Poland, Portugal, the United Kingdom, the Czech Republic, Romania and Turkey.
Since the end of the Cold War, more than a dozen former Eastern Bloc countries, including three former Soviet republics, have joined the alliance.
Russia continues to view NATO as a threat despite the collapse of the Soviet Union.
Amid recent tensions with the West, Russia has asked for firm guarantees that the alliance will not expand further, something NATO members have resisted.
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However, since May 20222 more tension has built up between NATO and Russia due to Finnish President Sauli Niinisto and Prime Minister Sanna Marin's declaration of support for NATO after the Finnish government presented recently to the country's parliament a report on national security outlining the path to joining the alliance as one of Finland's options, amid Russia's war in Ukraine.
Finland and Sweden submitted their applications to join NATO in May.
All 30 NATO members must give their unanimous approval for a country to be accepted into the alliance.
What does the NATO principle of collective defense mean?
Despite the great geopolitical changes that have occurred since NATO's founding, its objective remains the same.
The key principle on which the alliance is based is that of collective defense: "An armed attack against one or several of them in Europe or North America will be considered an attack against all of them."
The principle of collective defense is included in article 5 of the North Atlantic Treaty.
It guarantees that the resources of the entire alliance can be used to protect any member nation.
This is crucial for many of the smaller countries, which would be helpless without their allies.
Iceland, for example, does not have a standing army.
Since the United States is the largest and most powerful member of NATO, any state in the alliance is effectively under the protection of the United States.
Actually, the first and only time that article 5 was invoked was after the attacks of September 11, 2001 against the United States;
as a consequence, NATO allies joined the invasion of Afghanistan.
However, NATO has also acted on other occasions.
It launched collective defense measures in 1991 when it deployed Patriot missiles during the Gulf War, in 2003 in the midst of the Iraq crisis, and in 2012 in response to the situation in Syria, also with Patriot missiles.
All three were based on requests from Turkey.
Does NATO have its own army?
No. NATO depends on the contribution of forces from its member countries, which means that it is essentially only as strong as the individual forces of each nation.
It is in the interest of the entire coalition to ensure that each country devotes sufficient resources to its defense.
This has been one of the main sticking points in the alliance, with the US and UK often criticizing other member states for not doing their fair share.
US military spending has always dwarfed the budgets of other allies since NATO's founding in 1949. But the difference became much greater when the US increased its spending after the 9/11 attacks.
Under NATO guidelines, each country should spend 2% of its GDP on defense, but most countries are falling short of that goal.
Former US President Donald Trump was particularly vocal on this issue, demanding that European countries do more and, at one point, even suggesting that they "pay back" the US for its past deficits.
According to the most recent NATO estimates, seven member states – Greece, the United States, Croatia, the United Kingdom, Estonia, Latvia, Poland, Lithuania, Romania and France – would reach the 2% target by 2021.
Still, this is a significant improvement.
In 2014, only the US, the UK and Greece spent more than 2%.
At that time, all member countries below the threshold committed to increasing military spending to reach the goal in a decade.
Most are keeping their promise.
How has NATO's role changed over time?
After the fall of the Soviet Union, NATO evolved and expanded.
Since then its members have served as peacekeepers in Bosnia, have fought against human trafficking and have been deployed to intercept refugees in the Mediterranean.
The Alliance is also responding to the new ways in which conflicts can play out, for example by creating a cyber defense center in Estonia.
CNN's Frederik Pleitgen and Nadine Schmidt contributed to this report.
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