In a momentous day for the Nordic nations, Finland said yesterday that it would formally apply for Nato membership in the coming days, while the ruling Social Democrats in Sweden said they would follow suit, breaking 200 years of military non-alignment. Finnish president Sauli Niinist? called it a “historic day”, saying “a new era is opening”.

Their potential accession would transform the security architecture in northern Europe and make it easier for the alliance to defend the Baltic countries. It would also more than double the length of Nato’s border with Russia, which has threatened “serious military and political consequences” should either country join the alliance.

Finnish prime minister Sanna Marin said: “We cannot trust any more that there will be a peaceful future next to Russia on our own. That’s why we’re making the decision to join Nato: it’s an act of peace, to make sure there will never again be a war in Finland in the future.”