NATO is a European and North American defense alliance set up to promote peace and stability and to safeguard the security of its members. It was created as the Cold War escalated and is headquartered in Brussels, Belgium.
The aim of the United States-led alliance was to protect Western European countries from the threat posed by the Soviet Union and to counter the spread of Communism after World War II.
Here’s what you need to know.
Twelve founding countries — the United States, Canada, the United Kingdom, France and eight other European nations — signed the North Atlantic Treaty in 1949, pledging to protect each other by political and military means.
Over the decades since, the alliance has grown to include a total of 30 members.
In alphabetical order, they are: Albania, Belgium, Bulgaria, Canada, Croatia, Czech Republic, Denmark, Estonia, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Lithuania, Luxemburg, Montenegro, the Netherlands, North Macedonia, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Turkey, the UK and the US.
Ukraine is not a member of NATO, but has long hoped to join the alliance. This is a sore point for Russia, which sees NATO as a threat and vehemently opposes the move.
But the US and NATO have resisted those demands. The alliance has always had an “open door policy,” which states that any European country ready and willing to undertake the commitments and obligations of membership is welcome to apply for membership. Any decisions on enlargement of the alliance must be agreed unanimously.
Following the end of the Cold War, NATO made it clear it would welcome expansion to the east and in 1997, Czech Republic, Hungary and Poland were invited to begin accession talks.
Since then, more than a dozen countries from the former Eastern bloc, including three former Soviet republics, joined the alliance.
Despite the major geopolitical changes since NATO’s foundation, its stated purpose remains the same. The key principle underpinning the alliance is one of collective defense: “An armed attack against one or more of them in Europe or North America shall be considered an attack against them all.”
What does that mean in practice?
The principle of collective defense is laid out in Article 5 of the North Atlantic Treaty. It guarantees that the resources of the whole alliance can be used to protect any single member nation. This is crucial for many of the smaller countries who would be defenseless without its allies. Iceland, for example, has no standing army.
Since the US is the largest and most powerful NATO member, any state in the alliance is effectively under US protection.
In reality, the first and only time Article 5 has been invoked was in the aftermath of the September 11, 2001 attacks on the US; as a result, NATO allies joined the invasion of Afghanistan.
However, NATO has taken action on other occasions too.
It put collective defense measures in place in 1991 when it deployed Patriot missiles during the Gulf War, in 2003 during the crisis in Iraq, and in 2012 in response to the situation in Syria, also with Patriot missiles.
All three were based on requests from Turkey.
Does it have its own army?
No. NATO relies on its member countries contributing forces, meaning it is essentially as strong as the individual forces of each nation. It is in the interest of the entire coalition to make sure each country is putting enough resources into its defense.
This has been one of the main sticking points in the alliance, with the US and the UK often criticizing other member states for not putting in their fair share.
American military spending has always eclipsed other allies’ budgets since NATO’s founding in 1949. But the gap grew much wider when the US beefed up its spending after the 9/11 attacks.
Under the NATO guidelines, each country should be spending 2% of its GDP on defense, but most countries are not reaching that target.
Former US President Donald Trump was particularly vocal on this topic, demanding European countries do more and at one point even suggesting they “repay” the US for their past shortfalls.
According to the most recent estimates from NATO, seven member states, Greece, the US, Croatia, the UK, Estonia, Latvia, Poland, Lithuania, Romania and France hit the 2% goal in 2021.
Still, this is a significant improvement. In 2014, only the US, the UK and Greece were spending more than 2%.
At that time, all member countries that were below the threshold, committed to ramp up military spending to reach the target within a decade. Most are sticking with the promise.
How has the organization’s remit changed over time?
After the collapse of the Soviet Union, NATO evolved and expanded.
Over the years since, its members have served as peacekeepers in Bosnia, fought against human trafficking, and been deployed to intercept refugees in the Mediterranean.
The alliance is also responding to the new ways conflicts can unfold, for example by setting up a cyber defense hub in Estonia and, in 2019, recognizing space as a new operational domain.
What’s it doing about the Ukraine crisis?
As Russia has massed tens of thousands of troops near the Ukrainian border in recent weeks, NATO has sought to boost its presence in eastern member states.
According to NATO, there are four multinational battalion-size battlegroups in Estonia, Latvia, Lithuania and Poland, on a rotational basis.
NATO Secretary General Jens Stoltenberg said the alliance is prepared to rapidly reinforce that presence further by sending additional forces and capabilities into the area.
The Biden administration has put as many as 8,500 US troops on heightened alert for a possible deployment to eastern Europe.
More immediately, several NATO countries have started sending weapons and ammunition to Ukraine.
The US has sent two shipments of weapons to Ukraine, including 300 Javelin anti-tank missiles, 800 bunker-busting bombs and hundreds of thousands of rounds of ammunition. The UK has supplied Ukraine with new light anti-tank weapons, and the Czech government agreed on Wednesday to donate more than 4,000 152-millimeter caliber artillery shells.
NATO does not have any troops in Ukraine, and no plans have been announced to send troops from the alliance into the country.
But although Ukraine is not a NATO member, the alliance also provides strategic-level advice to the country and has described the relationship as “one of the most substantial of NATO’s partnerships.”
Since Russia annexed the Ukrainian peninsula of Crimea in 2014, the alliance has launched a number of projects to support Ukraine’s capacity-building in key areas, including cyber defense, logistics and the modernization of the nation’s command and control. Since then it has also implemented what it said was the biggest increase in collective defense since the end of the Cold War, ramping up its presence in member states closest to Russia.
Why is Germany being criticized?
Berlin has come under criticism recently for its policy of not exporting weapons to crisis areas.
Germany has so far refused to send arms to Ukraine, promising instead to give Kyiv a field hospital, medical training and 5,000 military helmets.
Germany’s complicated history means its governments have always been cautious about military spending and the idea of getting directly involved in a conflict is a difficult one to sell there.
It has also been criticized for failing to reach the 2% GDP spending target, along with other countries. As Europe’s largest economy, Germany is already NATO’s third biggest net spender on defense. In 2021, it invested an estimated $64 billion into defense, trailing only behind the UK, which spent $72 billion, and the US which poured $811 billion into its defense — more than twice the total amount spent by all other NATO members.
The new German government has committed to increasing spending further to reach NATO’s 2% goal, but it has stood firm on the issue of weapons exports.
“The German government has very clearly agreed that we will not send any lethal weapons, or arms deliveries to conflict areas because we do not want to fuel these conflicts further,” German Defense Secretary Christine Lambrecht said Thursday.
Germany hosts more than 30,000 US military forces and their families. It is also one of several NATO countries to host US nuclear weapons on its soil.
The UK came to Germany’s defense on the issue on Thursday, with British Defense Secretary Ben Wallace saying his country doesn’t judge Germany for its decision.
“The advantage of being in NATO is there are 30 allies, so we can all assist Ukraine in our own way,” he said.
”Obviously, the United Kingdom has taken a view that lethal aid of a tactical defensive nature is something that the Ukrainians need, but we’re not sitting in judgement over other countries,” Wallace said.
CNN’s Frederik Pleitgen and Nadine Schmidt in Berlin contributed reporting.