Finland joined Nato: Here is what you need to know

At a ceremony in Brussels, Finland's foreign minister, Pekka Haavisto, signed an accession paper and gave it to the US Secretary of State, Antony Blinken, making Finland the organisation's 31st member. As Finland joined Nato, Moscow issued a warning that if required, it will strengthen its defences in the area.

The handover completes an expedited application process begun last May when Finland and neighbouring Sweden abandoned decades of military nonalignment to seek security as Nato members in the wake of Russia's invasion of Ukraine. The handover signifies the formal accession of Russia's western neighbour to the largest military alliance in the world.

“President Putin had as a declared goal of the invasion of Ukraine to get less Nato,” the alliance’s secretary general, the former Norwegian prime minister Jens Stoltenberg, said shortly before the ceremony, reported The Guardian. “He is getting exactly the opposite.”

Stoltenberg added: “Finland today, and soon also Sweden will become a full-fledged member of the alliance.” Finland’s membership “removes the room for miscalculation in Moscow about Nato’s readiness to protect Finland”, he said.

Outside of NATO headquarters, Finland's blue and white flag will soon be hoisted alongside that of its allies.

After Finland's membership, Nato's border with Russia will nearly quadruple. Finland and its eastern neighbour share a 1,340 km (832 mi) border, as seen in the map of Finland and Russia. 

Moscow has issued a warning that if required, it will strengthen its defences in the area.

Putin threatened to install tactical nuclear weapons in Belarus last month, but Stoltenberg downplayed the threat, saying Nato had "not seen any changes in Russia's nuclear posture that need any adjustments in our stance, but we will stay watchful."

This Monday, Turkey became the final Nato member to ratify Finland's application, however, Sweden's application is still being held up by Hungary and Turkey because Ankara accuses Sweden of harbouring Kurdish militants and Budapest is upset by Swedish criticism of Hungary's rule of law.

The day of Finland's admission marks the 74th anniversary of the Washington Treaty, which established Nato.

The Nato expansion to include Finland, according to the Kremlin's spokesperson Dmitry Peskov, is an "encroachment on our security and Russia's national interests," and Moscow will closely monitor any Nato military deployments there, he added.

The foreign ministry said that the country will have to take "retaliatory measures" to counter the threats to its national security coming from Finland's membership in Nato.

It added that the situation in Northern Europe, which has been "one of the most stable regions in the world" will change with this development.

By becoming a member of NATO, Finland is subject to Article 5, which states that any attack on one member "will be regarded as an attack against them all."

With one of Europe's greatest artillery arsenals and a wartime population of 280,000, the nation joins the alliance as a powerful military force.

Was Finland part of Russia?

The event marks the end of an era of military non-alignment for Finland that began after the country repelled an invasion attempt by the Soviet Union during World War Two and opted to try to maintain friendly relations with neighbouring Russia.

But the invasion of Ukraine in February 2022 prompted Finns to seek security under NATO's collective defence pact, which states that an attack on one member is an attack on all.

Moscow, which long criticised the move, reacted crossly.

Since the end of the Cold War three decades ago, Moscow has watched successive waves of Nato enlargement to the formerly communist east of Europe with consternation, and the issue was a bone of contention even before the invasion of Ukraine.

People in the Russian city of St Petersburg, only out 150 km (93 miles) from the Finnish border, said Finland could be making problems for itself by joining Nato.