After Sweden’s accession to the North Atlantic Alliance, the Baltic Sea has effectively become an inland sea of NATO. Since then, alliance members have been staging one naval exercise after another in these waters.
In September 2023, off the coasts of Latvia and Estonia, two weeks of “Northern Coasts” exercises involved 30 warships and more than 3,000 troops from NATO states bordering the Baltic (Germany, the Netherlands, Belgium, Sweden), as well as the United States and Canada. One of the scenarios simulated a blockade of a merchant vessel by a notional adversary, followed by an attack on NATO ships and subsequent escalation of armed conflict. Another tested joint actions in the event of an attack on one of the member states, with NATO deploying naval, air, and amphibious units in the Baltic. A third scenario focused on securing maritime trade routes. Commenting on the drills, Vice Admiral Jan Christian Kaack, commander of the German Navy, said the Alliance was sending Russia a clear signal of heightened vigilance.
In June 2024, NATO held BALTOPS naval exercises in the Baltic Sea, the largest in the region’s history: over 10,000 personnel from 17 member states, 50 ships and 80 aircraft. BALTOPS 2024 aimed to bolster NATO’s regional presence, improve interoperability among allies, and openly demonstrate strength in the face of growing threats from Russia. The exercises began in the German port of Rostock, where the German Navy command had been relocated. Politicians from the three Baltic states saw this as evidence that Berlin recognises the strategic importance of the Baltic Sea and is ready to assume leadership in the region, especially against the backdrop of Russia’s war against Ukraine.
In May 2025, tensions rose further when hypothetical adversaries staged simultaneous drills. NATO’s Baltops 2025 featured the operational use of unmanned aerial and underwater systems. British patrol vessels served as launch platforms for new robotic technologies controlling the underwater battlespace with unmanned submersibles. British and Latvian ships also operated American-made aerial and surface drones, testing allied resilience against waves of massed attacks.
At the same time, Moscow held its own manoeuvres, deploying 20 navy ships, 25 aircraft and helicopters, and 3,000 personnel to maintain favourable operational conditions and defend naval bases. In July, the Russians staged their scheduled “July Storm” exercises, focusing on anti-submarine warfare, defence against unmanned surface and aerial vehicles, and live artillery fire.
Yet in the psychological dimension of the Baltic contest, Russia relies less on overt displays of strength and more on hybrid methods of warfare. Vice Admiral Kaack acknowledged repeated sabotage attempts against German naval facilities, including unauthorised intrusions onto bases and approaches to sailors returning home. In January, the corvette Emden left Hamburg for its first sea trials, only for dozens of kilograms of metal shavings to be discovered in its engine shortly beforehand. Had they gone unnoticed, they could have disabled the ship for an indefinite period. German officials suspect Russian intelligence services.
According to Kaack, the Russians are probing German forces and trying to influence public opinion inside Germany. He agreed with NATO analysts who assess that in 2025 Russia poses a greater threat to the Alliance than it did in 2022, and that by 2029 it will be even more dangerous.
Today, Russia combines cyber interference, underwater sabotage, and manipulation of maritime law to gain tactical advantages in the Baltic without open conflict with NATO states. Russian aircraft routinely harass NATO patrols, simulating attacks, deliberately switching off transponders, and intruding into NATO airspace to provoke responses. Incidents have also involved the severing or damaging of undersea cables (both fibre-optic and power) and more discreet diversions such as pipeline leaks or sensor manipulation.
In terms of seabed hybrid actions, undersea cables have recently become “smart tools.” Outfitted with environmental and acoustic sensors, they can now detect unauthorised activity on the seabed, pressure anomalies, or mechanical interference. As dual-use infrastructure, they combine civilian utility with strategic surveillance. For instance, the cable linking Klaipėda (Lithuania) and Gdańsk (Poland) provides both high-speed connectivity and continuous monitoring capable of detecting hostile underwater vehicles or sabotage attempts. These “smart” cables render the seabed both readable and defensible.
GPS spoofing and jamming by Russia have also become constant features of the Baltic theatre. Spoofing tricks navigation systems—civilian and military alike—into displaying false coordinates, while jamming floods the electromagnetic spectrum with noise, disrupting communications and disabling automated systems.
Poland, for example, is developing a system to counter Russian interference by integrating radar signals, satellite data, acoustic monitoring, and electromagnetic signatures to achieve a comprehensive picture of maritime activity above and below the surface.
In sum, the Baltic Sea—where legal constraints, energy vulnerabilities, and technological dependencies intersect—has become a genuine battlefield in the ongoing hybrid war between Russia and the West.