Why NATO formed and why Finland and Sweden want to join the alliance

Erin Doherty

Data: NATO; Map: Thomas Oide/Axios

Russian President Vladimir Putin has repeatedly pointed to NATO's post-Cold War enlargement as one of the many reasons for his invasion of Ukraine. But Russia's war has ultimately pushed the alliance on a path to further expansion.

The latest: Formally submitting applications last month, Finland and Sweden are poised to soon join NATO. Their future accession became even more likely on Tuesday after Turkey lifted its objection to the two Nordic countries joining the alliance.

The big picture: Finland and Sweden's membership would dramatically change the security landscape in Europe and more than double the length of the alliance's borders with Russia.

It will be NATO's ninth enlargement since its founding in 1949.

Below is a brief look at why NATO formed, why Finland and Sweden are seeking membership, and where the alliance's likely expansion leaves Russia and Ukraine.

Why was NATO formed?

The North Atlantic Treaty Organization, or NATO, was created in 1949 by 12 countries, including the U.S., Canada and other Western European countries, to provide collective security against the Soviet Union.
Since the fall of the Soviet Union, NATO has more than doubled in size to include 28 European countries, Canada and the U.S.
Today, NATO's stated purpose is "to guarantee the freedom and security of its members through political and military means."

When does NATO act militarily?

Article 5 — which stands at the heart of NATO's founding treaty — says that an attack on any member of the alliance should be viewed as an attack on all members.
If such an attack does occur, each member will take "measures necessary to restore and maintain international peace and security," according to the treaty.

Article 5 has been invoked just one time in history — after the terrorist attacks on Sept. 11, 2001, when the alliance launched aircrafts to help patrol the skies over the U.S.

How do countries join NATO?

A country seeking to join the mutual-defense alliance must demonstrate that they meet political, economic and military goals and that they will both contribute and benefit from NATO's collective security.
Requirements for entry include having a functioning democratic political system based on a market economy, fair treatment of minority populations and a commitment to democratic civil-military relations, according to the alliance.
All 30 NATO member states must support a country's membership.

Why do Finland and Sweden want to join?

Finland and Sweden have for decades been NATO's closest partners, despite their official "non-alignment."

Public support for NATO membership in the Nordic countries shot up virtually overnight after Russia invaded Ukraine, with a strong majority in both countries now in favor of joining the alliance, Axios' Zachary Basu writes.

Finland's President Sauli Niinistö says his country is seeking NATO membership because Russia's invasion proved that the Kremlin does not respect officially non-aligned countries.

"What we see now, Europe, the world, is more divided," Niinistö told CNN. "There's not very much room for nonaligned in between."

Sweden's Prime Minister Magdalena Andersson also pointed to Russia's actions.

"Russia's unprovoked invasion of Ukraine is not only illegal and indefensible, it also undermines the European security order that Sweden builds its security on," Andersson said in a speech on Sunday.
"Should Sweden be the only country in the Baltic Sea region that was not a member of NATO, we would be in a very vulnerable position. We can't rule out that Russia would then increase pressure on Sweden," she warned.

NATO Secretary-General Jens Stoltenberg previously said the two Nordic countries would be quickly "welcomed with open arms."

“All allies agree on the importance of NATO enlargement. We all agree that we must stand together, and we all agree that this is an historic moment which we must seize," Stoltenberg said Wednesday as Finland and Sweden submitted their applications. “This is a good day at a critical moment for our security."
Turkey's President Recep Tayyip Erdoğan had voiced opposition to the Finland and Sweden's membership, claiming they are home to Kurdish "terrorist organizations."
But on the sidelines of the NATO Summit in late June, Erdoğan signed a trilateral memorandum with the leaders of Finland and Sweden confirming Turkey would support their accession.

Ukraine and NATO

Ukraine, along with Georgia, sought to join NATO at the Bucharest Summit in 2008, viewing it as a route to independence from Russian influence, per the Washington Post.

The U.S. and several other NATO members supported the countries' membership, but Germany and France blocked the effort, arguing that Ukraine membership would outrage Russia. They also contended the two countries were not ready for membership.

In an attempted compromise, Germany and France said the two countries could become members — but did not specify when.
In the months that followed, Ukraine and Georgia's vague assurances of membership dwindled. Talks between Ukraine and NATO resumed at the end of 2008, but no specific Membership Action Plan (MAP) was announced, per the Post.

Ukraine's hopes of joining NATO were then dashed in 2010 when Viktor Yanukovych was elected president. After taking office, Yanukovych called joining the alliance an "unrealistic prospect."

Since Yanukovych was ousted from power in 2014, Ukraine has renewed its interest in joining NATO, including in 2017, when it adopted legislation making NATO membership a priority, but it hasn't advanced its bid for membership.
Ukrainian President Volodymyr Zelensky has accepted that his country will not join NATO, at least in the current moment. "It is clear that Ukraine is not a member of NATO. We understand this," he said in March.

Russia and NATO

Putin is staunchly opposed to Ukrainian membership in NATO, arguing that eastward expansion of the alliance would pose a threat to Russia's security.
The Russian president last month said that NATO "in essence, is engaged in a war with Russia through a proxy and is arming that proxy."
Putin has warned Finland and Sweden NATO membership would be a "mistake." He later said that "there is no direct threat to Russia in connection with NATO's expansion to these countries. But the expansion of [the alliance's] military infrastructure to these territories will certainly evoke a response on our part."

NATO forces and Ukraine

NATO is taking collective defense measures in response to Russia's invasion, without invoking Article 5.
Since Russia's military buildup on Ukraine's border began in October, the U.S. and NATO have deployed thousands of troops to eastern-flank countries like Poland, Lithuania, Latvia, Estonia, Bulgaria and Romania. The alliance last month deployed four new battle groups in the area.
NATO has also sent thousands of weapons to Ukraine throughout the invasion, including antitank weapons, artillery systems and helicopters.
Early in the war, NATO ruled out establishing a "no-fly zone" over Ukraine, despite repeated requests from Zelensky to establish one, fearing that it could mark a significant escalation and bring the alliance directly into a conventional conflict with a nuclear power.

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Editor's note: This story has been updated with new details from the NATO Summit in Madrid.