Putin's new Nordic nightmare: How strategically crucial Baltic Sea will become 'NATO's lake' after Sweden was cleared to join the alliance in huge blow for Kremlin regime

The strategically important Baltic Sea is being dubbed NATO's lake after Sweden was cleared to join the military alliance - strengthening its power in the region in a nightmare development for Vladimir Putin.

The country's accession to the alliance adds the final puzzle piece around the shores of the sea, which is a crucial maritime gateway for Russia, making it easier for NATO to exert control and reinforce its vulnerable Baltic states.

Analysts have suggested it will mean that Western allies, including the UK and United States, will be well-placed to strangle Russia's room for manoeuvre in the important shipping route if a war with Moscow ever breaks out.

But Moscow will still be able to threaten undersea infrastructure and menace the region from its bases near St Petersburg and in heavily-armed exclave Kaliningrad, with experts warning that NATO must remain alert to the Russian threat.

'If you look at a map then geographically the Baltic Sea is becoming a NATO lake, yes,' said Minna Alander a research fellow at the Finnish Institute of International Affairs. 'But there is still work to do for NATO.' 

NATO's power will be strengthened in the region in a nightmare development for Vladimir Putin (pictured today)

Swedish and Finnish soldiers perform war simulation exercises during the Baltic Operations NATO military drills (Baltops 22) on June 11, 2022

Swedish Prime Minister Ulf Kristersson and Hungary's Prime Minister Viktor Orban shake hands after a press conference following their meeting in Budapest, Hungary, on Friday

On Monday, Hungary became the final NATO member to approve the country's application from 2022 to join the alliance in response to Russia's invasion of Ukraine.

It was hailed as a 'historic day' by Swedish Prime Minister Ulf Kristersson, while NATO Secretary General Jens Stoltenberg immediately welcomed Hungary's ratification. 

'Sweden's membership will make us all stronger and safer,' Stoltenberg wrote on X.

'The parliaments of all NATO member states have now voted in favour of Swedish accession to NATO. Sweden stands ready to shoulder its responsibility for Euro-Atlantic security,' Kristersson said.

Sweden's NATO membership was supported by 188 lawmakers in Hungarian parliament, with 6 against and no abstentions.

Hungarian Prime Minister Viktor Orban's government has faced pressure from NATO allies to fall in line and seal Sweden's accession to the alliance.

After Finland joined last year, Sweden's membership - which cleared the final hurdle on Monday with Hungary's vote on ratification - means all the countries surrounding the Baltic Sea, except Russia, will be part of the military alliance.

Since Russia's invasion of Ukraine, a series of high-profile incidents involving pipelines and cables under the Baltic Sea have given NATO a wake-up call over its vulnerabilities.

In September 2022 a sabotage attack hit the Nord Stream gas pipelines between Russia and Europe. Over a year on, investigators have still not publicly named those responsible.

Then last October a gas pipeline and a cable from Finland and Sweden to Estonia were damaged. Finnish police say they believe a Chinese cargo ship was likely involved.

A resident prepares a damaged car to be towed, near a residential building damaged during a Russian drone strike, in Dnipro, Ukraine, on Monday

Putin listens to Defence Minister Sergei Shoigu taking part in the wreath laying ceremony at the Unknown Soldier Tomb, marking the Defender of the Fatherland's Day, on Friday

Swedish Prime Minister Ulf Kristersson speaks during a press conference with his Hungarian counterpart Prime Minister Viktor Orban following their meeting in Budapest, Hungary, on Friday

NATO has bolstered its naval deployments in response and is looking to step up its monitoring capabilities, but keeping an eye on what's happening beneath the water is a major task.

'It's very difficult to have overall control of a sea as you would control territories on land,' said Julian Pawlak, a researcher at Germany's Bundeswehr University in Hamburg.

'What the Nord Stream sabotages have shown, among others, is that it remains hard to be aware exactly what is happening below the surface and on the seabed.'

Sweden has long had a close partnership with NATO but its formal membership will allow it to be fully integrated into the alliance's defence plans.

Beyond its long Baltic coastline, Sweden brings with it the island of Gotland which would play a central role in helping NATO impose its will.

But just across the water Russia has its own vital outpost - the exclave of Kaliningrad.

Wedged between Poland and Lithuania, Moscow has in recent years turned the region into one of the most militarised in Europe, with nuclear-capable missiles stationed there.

Russia's Baltic fleet based in Kaliningrad is a shadow of what it was during the Cold War and the invasion of Ukraine has sapped some of its forces from the region.

But John Deni, a research professor at the US Army War College, said the Kremlin has kept up investments in undersea capabilities and still has the firepower to stage small-scale landings or threaten NATO supply routes.

'In terms of artillery, indirect fires and nuclear-capable weapons they out-gun and out-range NATO allies in the region,' Deni said. 

'Allies have to meet that threat and counter it.'

Swedish Prime Minister Ulf Kristersson and Hungary's Prime Minister Viktor Orban hold a press conference following their meeting in Budapest, Hungary, on Friday

On the other side, while Stockholm brings with it a rich heritage of naval history, like other NATO states in the area its sea power in the Baltic remains understrength.

'Even if you count Sweden, NATO naval assets are relatively limited,' Deni said, adding that the allies need to develop their ability to carry out demining under fire.

Three countries breathing a particular sigh of relief over the entry of Sweden - and Finland - are NATO's Baltic states, Estonia, Latvia and Lithuania, long seen as an Achilles heel for the alliance.

War planners have struggled to work out how to stop them being cut off if Russian land troops seized the 65-kilometre (40-mile) Suwalki Gap between Belarus and Kaliningrad.

Sweden's position, straddling both the North and Baltic Seas, opens up a key route for transiting more NATO forces to protect them in case of attack.

'It allows US forces to reinforce the Baltic Sea nations in a timely manner, but especially the frontline states,' said Tuuli Duneton, Estonian undersecretary for defence policy.

Despite the joy at NATO over welcoming Sweden to the fold, however, US academic Deni insisted the alliance should lay off considering the Baltic its own property.

'Calling it a "NATO lake" leads to complacency,' Deni said.

'The challenge and the threat posed by Russia in the region is significant in some ways and the allies for now lack the capacity to counter that in a crisis.'