Russia’s war in Ukraine has forced the Baltic states to prepare for what was once unthinkable: a direct military confrontation on NATO soil. Central to that planning is the Suwałki corridor — a narrow strip of land between Belarus and the Russian exclave of Kaliningrad that forms the alliance’s only land link to the Baltics.
Military planners have long viewed the narrow land bridge, which connects Poland to Lithuania, as NATO’s soft underbelly.
“If Russian forces were to seize it, Lithuania, Latvia and Estonia would effectively be cut off from reinforcements from other European NATO members,” Ben Hodges, a retired US general who commanded US forces in Europe, told The Parliament.
NATO’s weak point is once again in focus ahead of joint Russian-Belarusian military exercises — codenamed Zapad 2025 or “Exercise West” — planned for September. Similar exercises in 2017 and 2021 included simulations of an invasion of the Suwałki corridor — and Zapad 2025 is expected to again rehearse such a scenario. The exercises in 2021, experts say, helped prepare Russia for its full-scale invasion of Ukraine a year later.
Putin keeps the Baltics on edge
Since Russia invaded Ukraine in early 2022, the prospect of wider war in Eastern Europe has shifted from theoretical to highly plausible. For the EU's Baltic nations — once absorbed into the Soviet Union by force — the danger is deeply rooted in history.
“Russia has been a long-time enemy and we have learned lessons from history. We have a pretty good understanding of how this country actually acts and thinks,” Tomas Godliauskas, Lithuania’s vice-minister of defence, told The Parliament.
Russia's hybrid attacks across the Baltics and the rest of Europe have been mounting in recent years, including border provocations, covert operations at sea, cyberattacks and election interference.
“In the last couple of years, we’ve seen a palette of threats by Russia — the organised migration pressure from Belarus, sabotage events and Russia’s shadow fleet operating in the Baltic Sea,” Godliauskas said.
In May, the Estonian Navy intercepted a Russian ‘shadow fleet’ ship in the Baltic Sea — prompting a Russian jet to briefly violate NATO airspace to escort the vessel into Russian waters. For officials in the region, the message is clear: Moscow’s ambitions extend beyond Ukraine.
“When Russia reconstitutes its forces, the Baltic states become the most vulnerable part of NATO,” Tomasz Szatkowski, Poland’s ambassador to NATO from 2019-2024, told The Parliament. “And if the Russian plan is to undermine the credibility of NATO, then again the Baltics are the most exposed part of NATO's frontier.”
In May, the Institute for the Study of War warned in a report that Russia was laying the ideological groundwork for future aggression. A week earlier, Russian Foreign Minister Sergey Lavrov’s endorsement of a book denying Lithuanian statehood sparked alarm across the region. For many officials, it signalled that Moscow could be preparing the narrative architecture to justify military action — just as Russian President Vladimir Putin’s pseudo-historical essay about Ukraine did ahead of the 2022 invasion.
The Baltics have also been on edge since President Donald Trump’s return to power in the US, according to Hodges. While Trump last month recommitted to NATO’s Article 5 guarantee to defend other member states from outside aggression, his ambivalence about the alliance and defending Ukraine has led the region to plan for defence scenarios in which reinforcements are delayed or never arrive.
"For now, there's still an American regiment in Lithuania. We don't know for how long," Hodges said.
Amid that uncertainty, Russia could potentially launch an attack in the region to test the US allegiance to NATO, said John Deni, a professor of security studies at the US Army War College. “Russians have long wanted to splinter NATO and the Western Alliance,” he told The Parliament. “One way to do that would be to try military action in the Baltics and show that Article 5 commitment is not the paper that it's written on.”
Russia could claim a threat to Kaliningrad — the heavily militarised Russian exclave wedged between Lithuania and Poland — as justification for a military incursion in the Suwałki corridor, Deni argued, even if no such threat exists. That makes the 65-kilometre strip, which runs between Kaliningrad and Moscow-friendly Belarus, NATO’s most vulnerable geographical pressure point.
Infrastructure delays undermine NATO in east
To address the Suwałki corridor’s vulnerabilities, Lithuania is rebuilding 113 kilometres of road and multiple bridges to military standard. The work is part of a broader expansion of the Via Baltica, a north-south highway connecting Tallinn and Warsaw through the Suwalki corridor.
Rail Baltica — a new 870-kilometre railway line running from Poland to the Baltics also via the corridor — is under construction, with the aim of allowing for the easier movement of troops and hardware across borders.
The EU is covering a significant share of the costs. The European Commission this month granted an additional €295.5 million to the Rail Baltica project. And Defence Commissioner Andrius Kubilius has called for at least €70 billion in EU-wide infrastructure upgrades to support military mobility.
But progress is slow. Some sections of Rail Baltica may not be completed until 2035.
“The pace at which the Rail Baltica is to be completed is several years out, and we needed it yesterday,” said Deni.
Baltic defence push accelerates
At the same time, the Baltic states are rearming at speed. Lithuania, Latvia and Estonia have each pledged to raise defence spending to 5% of GDP by 2026 — well ahead of the 2035 deadline agreed at last month’s NATO summit — making them the top spenders among European NATO members. That adds up to billions in new procurement for artillery, drones, air defence and troop readiness.
Lithuania is also hosting a permanently stationed German brigade — the Bundeswehr’s first long-term foreign deployment since World War II — signalling what Lithuania's Godliauskas called a “collective defence approach” on the eastern front.
The three countries are also investing in fixed defences. In January, they launched the “Baltic Defence Line” — a sprawling network of bunkers, anti-tank obstacles, surveillance systems and supply depots. And, in a controversial step, all three withdrew from the Ottawa Treaty to allow the use of anti-personnel mines on national territory. Leaders in Vilnius and Tallinn have defended the move as “logical and necessary.”
Warsaw, meanwhile, is investing €2.5 billion in its “East Shield” programme, reinforcing its borders with Belarus and Kaliningrad with surveillance towers, drones, anti-intrusion systems and physical barriers.
Swedish respite for NATO?
Sweden’s accession to NATO in 2024 shifted the strategic map in the region. The alliance is now the dominant player in the Baltic Sea, from which it has the capacity to launch air or naval operations from multiple bases. Its positioning could also provide a partial alternative to the Suwalki corridor for transporting equipment and reinforcements, Hodges said.
But, he added, sea and air access are not substitutes for rapid land-based mobility. The fundamental weakness remains: if the Suwałki corridor is blocked, NATO’s ability to reinforce the Baltics by land could still be fatally compromised.
“These nations that are so worried the Russians are going to attack in the next two years still can’t solve how to get a railroad done,” Hodges said. “They point the finger at the EU or blame each other. But the Suwałki corridor is an area where we’ve got to improve the mobility — quickly.”
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