Far from improving security in Europe, there are worrying signs that the decision by Sweden and Finland to apply for Nato membership could exacerbate tensions on the continent. It is widely acknowledged that one of the causes of the Ukraine conflict is the Kremlin’s resentment at what it regards as Nato’s increased threat to Russian security as a result of the alliance’s enlargement since the end of the Cold War. Russian President Vladimir Putin has, in particular, been critical of Nato’s willingness to allow countries that formerly formed the Soviet Union to be granted membership to the security umbrella. The suggestion that Ukraine, a country with close cultural and historic ties to Moscow, might be granted Nato membership was a source of genuine concern for Moscow. The move, therefore, by Sweden and Finland – two strategically important countries that have long prided themselves on their neutral status – to formally apply for Nato membership is unlikely to improve relations with Moscow. On the contrary, the prospect has provoked a strong reaction in Moscow, with Russian Deputy Foreign Minister Sergei Ryabkov denouncing the decision as a "grave mistake". Speaking shortly after the Swedish and Finnish governments confirmed their intention, Mr Ryabkov warned that they should have “no illusions that we will simply put up with it". “The general level of military tension will increase, predictability in this area will become less. It is a pity that common sense is being sacrificed for some phantom ideas about what should be done in the current situation,” he said. The fall-out of the war is already being felt in the energy sector. For one, Russia has been insisting that, in future, so-called “unfriendly” countries pay for its gas supplies in roubles. The EU has resisted this move and called on member states not to comply with Moscow's demand. Finland is, meanwhile, concerned that Moscow will respond to its Nato application by cutting off gas supplies this month. The country imports most of its gas from neighbouring Russia, although it accounts for only about 5 per cent of its annual energy consumption. The emergency preparedness committee in Helsinki insists it is ready for the likely supply cut. While Russia’s strong reaction is unlikely to change policy in either country, their latest decision represents a remarkable turnaround in their outlook. Sweden’s neutrality dates back to the Napoleonic Wars in the early 19th century, while Finland’s stance is an outcome of its experience during the Second World War, when it was involved in fierce fighting against Soviet forces. In what became known as "Finlandisation", Helsinki during the Cold War pursued a strict non-aligned policy in order to avoid provoking Moscow. Even though Finland moderated its neutral stance following the collapse of the Iron Curtain, public support within the country remained lukewarm over the idea of joining Nato for the past three decades, with only 20-25 per cent of the population favouring it. Since the outbreak of the Ukraine war, however, the figure has shot up to a record high of 76 per cent, according to the latest opinion poll. In Sweden, meanwhile, 57 per cent said they were in favour of Nato membership. The war has prompted a significant shift in the positions of the two social democratic prime ministers, Sweden’s Magdalena Andersson and Finland’s Sanna Marin, whose parties have often stressed neutrality. Both leaders have said that their parties now back Nato membership, with both countries' parliaments debating the issue at length before deciding to press ahead with the application process. Their entry will no doubt strengthen the alliance, particularly its defensive posture in northern Europe and the Arctic region. It's no surprise, then, that Nato Secretary General Jens Stoltenberg has responded positively. “This is a good day at a critical moment for our security,” Mr Stoltenberg said upon receiving letters from the Finnish and Swedish ambassadors at the Nato headquarters in Brussels. “We all agree that we must stand together, and we all agree that this is an historic moment which we must seize. Every nation has the right to choose its own path.” The only obstacle to the entry has emerged in the form of an objection from Turkish President Recep Tayyip Erdogan. Under the terms of the Nato charter, all 30 members must unanimously give their approval for the membership of new countries, and Mr Erdogan has chosen to use the issue to revise Ankara’s historic grievances with both Sweden and Finland. According to Mr Erdogan, “neither of these countries have a clear, open attitude towards terrorist organisations", a reference to their attitude to the Kurdistan Workers’ Party, which Turkey views as a terrorist group – as do the US and EU. Ankara has previously criticised both Finland and Sweden for refusing to extradite suspects wanted in Turkey. Mr Erdogan is also annoyed with Sweden for imposing arms sanctions against Ankara in 2019 over its military operations in Syria. Nevertheless, Nato officials remain confident that Turkish objections can be overcome, paving the way for what will constitute one of the biggest geopolitical shifts in Europe since the fall of the Soviet Union.