What is NATO? The North Atlantic Treaty Organization explained

This article has been updated.

Ahead of its summit in June, the North Atlantic Treaty Organization (NATO) commissioned artist Vaskange to create a game - to find all 32 Member country flags hidden in an 'infinite' artwork.

The interactive experience reflects NATO’s growing membership, with the number of flags representing its expanding alliance.

NATO Allies will come together at The Hague from 24-25 June, amidst an escalating Israel-Iran conflict and an ongoing war in Ukraine, to discuss increased defence spending and deterrence mechanisms.

Ahead of the gathering, NATO Secretary General and former Dutch Prime Minister Mark Rutte delivered a speech in London, warning: "History has taught us that to preserve peace, we must prepare for war. Wishful thinking will not keep us safe. We cannot dream away the danger. Hope is not a strategy. So NATO has to become a stronger, fairer and more lethal Alliance."

Here's what you need to know about the Summit and the history - and future - of NATO.

NATO’s history is tied to Russian expansionism. It was created in 1949, in response to then premier of the USSR Joseph Stalin’s attempts to bring other states under communist rule.

The US, Canada, the UK, Belgium, Denmark, France, Iceland, Italy, Luxemburg, the Netherlands, Norway and Portugal signed a treaty stating that “an armed attack against one or more … shall be considered an attack against them all”.

It has since gone through nine rounds of enlargement: by the fall of the Berlin wall in 1989, there were 16 countries and in the 1990s, after the collapse of the USSR, former Soviet countries began joining.

Finland joined NATO in April 2023 followed by its neighbour Sweden, in March 2024, becoming the 32nd Ally, in what former Secretary-General Stoltenberg described as a "historic day".

"Sweden will now take its rightful place at NATO’s table, with an equal say in shaping NATO policies and decisions," Stoltenberg said. "Sweden’s accession makes NATO stronger, Sweden safer and the whole Alliance more secure. Today’s accession demonstrates that NATO’s door remains open and that every nation has the right to choose its own path.”

Both Sweden, and Finland, which has a 1,340km border with Russia, dropped their traditional stance of neutrality and applied to join NATO after the Russian invasion of Ukraine in 2022.

Georgia, Bosnia and Herzegovina are in the application process, alongside Ukraine.

The Madrid Summit Declaration in June 2022, reaffirmed NATO’s commitment to allow any European country to apply to join.

This "open door policy" is based on Article 10 of NATO's founding treaty - to join, countries have to commit to defence spending of at least 2% of GDP, alongside other measures.

But that figure is being debated and will be a key topic at the Summit in The Hague, where heads of state are expected to agree a new defence investment plan.

US President Donald Trump has called for 5% of member countries' GDP to be spent on defence, while Rutte has proposed Allies increase spending to 3.5% of GDP and commit a further 1.5% to broader security-related spending, Reuters reports.

State-based armed conflict was identified as the top immediate risk for 2025, by nearly a quarter (23%) of risk officers surveyed for the Forum's Global Risks Report 2025, reflecting heightened geopolitical tensions and fragmentation globally.

It now ranks as the third biggest risk over the coming two years, up from fifth position in 2024.

"From conflicts to climate change, we are facing interconnected crises that demand coordinated, collective action," said Mark Elsner, the Forum's Head of the Global Risks Initiative.

“Renewed efforts to rebuild trust and foster cooperation are urgently needed. The consequences of inaction could be felt for generations to come."