A tectonic shift in Europe’s security architecture caused by Russia waging war on Ukraine has led to Sweden and Finland going hand in hand to apply for membership in Nato. This may lead to a further hardening of Vladimir Putin’s attitude, seen already as excessively belligerent, though the Russian leader’s immediate response seemed muted enough after having earlier fulminated against the move. But that could change once military infrastructure, including possibly nuclear arms, is put up in the two countries.

Finland’s security concerns are understandable given that it shares a 1,300 km border with Russia’s northwest. Sweden believes joining the US-led club for mutual defence would strengthen security in Sweden and the Baltic Sea region even as it displays Nordic solidarity with its eastern neighbour, Finland. They are a natural fit to seek the security guarantee of Article 5 of Nato’s founding treaty by which an attack on one member is taken as an attack on all.

The expansion of Nato to 32 countries might hinge on Turkey accepting the proposal as it had objected to the new applicants on the grounds that they had hosted Kurdish militant groups and imposed arms embargoes on Ankara in 2019 over Turkey’s role in the Syrian war. The West believes Recep Tayyip Erdogan may be posturing only for domestic political gains ahead of next year’s elections and that he could be brought around to agree to the unanimity Nato seeks to admit new members.

The return of the Cold War was signalled the day Mr Putin ordered the invasion (Feb. 24) and the likely expansion of Nato is a corollary in the wake of the war. What effect this latest provocation, as Mr Putin sees it, will have on the ongoing “special military operations” in Ukraine, which he still justifies as a manoeuvre to help Russia “feel safe, develop and exist”, will have on the scale of Ukrainian operations is anybody’s guess.

If Mr Putin were to declare a full-scale war on Ukraine — despite events on the ground not having gone exactly Russia’s way except in its conquest of Mariupol this week with about 1,000 Ukrainian soldiers in the Azovstal steel plant surrendering — the world could be in for its greatest challenge since the days of interventions by the West and Russia in the Middle East. The aftereffects of the war have been explosive enough already for the global economy and fears will only grow over the return of reason.