Sweden joins Nato: What does this mean for the West's relationship with Putin?

Sweden officially became the 32nd member of NATO on Thursday, ending decades of post-World War II neutrality.

It joins the transatlantic military alliance as concerns about Russian aggression in Europe have spiked following the country's invasion of Ukraine in 2022.

US Secretary of State Antony Blinken, who presided at a ceremony with Swedish Prime Minister Ulf Kristersson, described it as a "historic moment" for Sweden.

"It's historic for alliance. It's history for the transatlantic relationship,” Mr Blinken said. “Our NATO alliance is now stronger, larger than it’s ever been.”

"Swedes realised something very profound: that if Putin was willing to try to erase one neighbour from the map, then he might well not stop there," he added.

The White House said that having Sweden as a NATO ally “will make the United States and our allies even safer.”

"NATO is the most powerful defensive alliance in the history of the world, and it is as critical today to ensuring the security of our citizens as it was 75 years ago when our alliance was founded out of the wreckage of World War II,” it said in a statement.

Prime Minister Rishi Sunak followed suit, as he congratulated and welcomed Sweden in a video.

After months of delay, Turkey ratified Sweden’s admission earlier this year, and Hungary did so in late February.

Sweden followed in Finland's footsteps, as the Nordic country abandoned its long-standing military neutrality last year in favour of joining NATO.

Before Finland and Sweden joined the US-led alliance, Russian President Vladimir Putin was quoted by his country's news agencies as saying he couldn't rule out tensions with the the Nordic nations if they were to join NATO.

“If military contingents and military infrastructure were deployed there, we would be obliged to respond symmetrically and raise the same threats for those territories where threats have arisen for us,” he told a news conference in the Turkmenistan capital of Ashgabat in 2022.

“If Finland and Sweden wish to, they can join. That’s up to them. They can join whatever they want.”

The accessions of Sweden and Finland, which shares a 1,340 km border with Russia, are the most significant additions to NATO in decades and come as a blow for the Russian president, who has sought prevent any further strengthening of the alliance.

What is NATO?

NATO stands for North Atlantic Treaty Organisation and is a collection of now 32 member states that work together in keeping the North Atlantic area safe.

The alliance was founded by 12 countries, including the United Kingdom, United States, Canada and Italy, in 1949 as a counterbalance to the burgeoning Soviet Union and a preventative measure against a resurgence of Nazi Germany.

Since then 21 other countries have joined in several rounds of enlargement.

NATO members hold frequent summits to discuss important issues and negotiate strategies for tackling international problems.

Ukraine has been trying to join the alliance since 2022, with the support of some members such as the United Kingdom, but leaders of the allied nations say there are still "conditions" that need to be met before the war-torn country can join.

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