Why Nato was formed and how Trump's Greenland push tests the alliance

As Donald Trump revives calls for US control of Greenland, Nato faces rare internal strain. Here's how the alliance was born, how its role evolved, and why allies are alarmed

US President Donald Trump’s renewed push for American control of Greenland has triggered unusually blunt warnings in Europe about stress-testing Nato’s core bargain: that allies do not threaten one another. Trump has floated options to acquire the island, either through a purchase or military action, a possibility Danish Prime Minister Mette Frederiksen has said would mean “the end of Nato”.

 

As the future of Nato is tested by the US President’s stance, here is a look back at the alliance’s Cold War origins and its evolving mission amid new internal strains.

 

Why Nato was formed

 

The North Atlantic Treaty Organisation or Nato was created in the aftermath of World War II as Western democracies confronted the growing threat from the Soviet Union. In April 1949, 12 countries led by the United States, the United Kingdom and France signed the North Atlantic Treaty. 

 

 

At its core was Article 5, which states that an armed attack against one member would be treated as an attack against all. This collective defence pledge, which is often described as 'one for all, all for one', became the foundation of Western security during the Cold War and acted as a deterrent against Soviet expansion.

 

Nato expanded early in its history. Greece and Turkiye joined in 1952, followed by West Germany in 1955. That same year, the Soviet Union and its allies responded by forming the Warsaw Pact, cementing the division of Europe into rival military blocs.

 

From the Cold War to the post-9/11 era

 

The collapse of the Soviet Union in 1991 raised questions about Nato’s relevance, but the alliance adapted rather than dissolving. During the 1990s, Nato undertook its first operations outside member states, intervening in the Balkans to stop violent conflicts in the former Yugoslavia.

 

It also began expanding eastward. In 1999, Poland, Hungary and the Czech Republic became the first former Warsaw Pact countries to join Nato. Further enlargement followed in the 2000s, bringing in the Baltic states and several eastern European nations, including former Soviet republics.

 

Nato invoked Article 5 for the first time after the September 11, 2001 terrorist attacks on the United States. Allies deployed forces to Afghanistan under a Nato-led mission, marking a shift beyond the alliance’s original focus on Europe. In the years that followed, Nato’s role expanded to include counterterrorism, cyber defence and crisis management operations well beyond the North Atlantic region.

 

Why Trump wants Greenland

 

Trump has repeatedly framed Greenland as a "national security" issue, arguing that US control of the island is necessary to counter Russian and Chinese influence in the Arctic.

 

Speaking to NBC News, Trump said Greenland was “very important” for the security of the United States, Europe and the wider “free world”. The White House has confirmed that a range of options are under discussion, including, according to Reuters, possible lump-sum payments of $10,000 to $100,000 per person to Greenland’s population of about 57,000.

 

Last week, White House Press Secretary Karoline Leavitt said the use of the US military was "always an option" at the President’s disposal.

 

What Nato allies have said

 

Denmark has rejected the idea outright. Frederiksen has said it “makes no sense” to suggest the US needs to take over Greenland and has urged Washington to stop issuing “threats against a historically close ally”. She warned that military aggression against Greenland would undermine Nato itself.

 

On January 6, seven Nato members — France, the UK, Italy, Spain, Germany, Poland and Denmark — issued a joint statement affirming that “Greenland belongs to its people” and that only Denmark and Greenland can decide its future.

 

The statement added that security in the Arctic must be pursued by Nato allies by upholding the principles of the UN Charter, including sovereignty, territorial integrity and the inviolability of borders.

 

Seven decades after its formation as a shield against an external adversary, Nato now faces a rare challenge from within. Trump’s interest in Greenland has forced the alliance to confront fundamental questions about trust and solidarity, which have underpinned Nato since its creation.