On 7 October 2023, the EE-S1 submarine communications cable between Estonia and Sweden was damaged, with four of the six fiberoptic cable pairs destroyed. A couple of hours later on the same day, the natural gas pipeline Balticconnector between Estonia and Finland was cut and put out of use for six months, probably by the same ship. The C-Lion1 submarine communications cable between Finland and Germany was damaged in November 2024 and went down again in December 2024 in connection with damage to the Estlink 2 submarine power cable cutting, for which the oil tanker Eagle S was suspected. Estlink 2 was repaired by June 2025. Such damage is not unheard of, globally there are usually about sixty cases a year—but such a concentration of accidents in both time and space, in the current geopolitical situation in which Russia is increasingly working to overturn the European security order, is suspicious despite the lack of hard evidence of Moscow’s deliberate involvement—other than that all involved ships are part of Russia’s shadow fleet. As a result of these incidents, NATO launched Operation Baltic Sentry on 14 January 2025 to improve maritime security in the Baltic Sea, safeguard the undersea cables and pipelines, and ensure Baltic energy and communications security.
Energy security is a particular concern for the Baltic States for geopolitical reasons. Having been occupied by the Soviet Union from 1945-1990, the three Baltic States were integrated into the Soviet energy infrastructure. This was reconfirmed in 1998 with the signing of the BRELL agreement, which kept the Baltic States’ energy systems synchronized with Russia and Belarus, remaining a major Baltic vulnerability even after joining the EU and NATO in 2004. During this time, Russia had not been shy to use gas as a weapon particularly against Latvia and Lithuania when they made policy decisions of which Moscow disapproved; this danger waned after Lithuania built a liquefied natural gas terminal at Klaipėda in 2014.
In February 2025 the Baltic States disconnected from BRELL and synchronized with the Continental European Network (CEN), finally connecting to Europe also in energy infrastructure after an 18 year long political and technical process which began in 2007 when Baltic prime ministers affirmed their aspiration to join CEN. Having finally achieved energy independence from Moscow, the Baltic States nonetheless remain vulnerable in a different way as their connection to CEN relies on a small amount of critical infrastructure: Estlink 1 and 2 connecting Estonia and Finland; Nordbalt connecting Lithuania and Sweden; and the LitPol Link between Lithuania and Poland.
This sparse infrastructure is a vulnerability. As the incidents of 2023 and 2024 demonstrate, it is perhaps trivial to disrupt provision of energy to, and thereby the energy security of, the Baltic States with a few well placed acts of sabotage. For example, at time of damage, Balticconnector was transporting 30GWh/day from Finland to Estonia, although it is bidirectional and also allows Finland to tap into Latvia’s strategic gas reserve at Inčukalns—such damage equally represents a danger to Finland. Damage to Estlink 2 led to a decrease in provision of electricity from Finland to Estonia from 1,016 MW to just 358 MW. With the exception of the LitPol Link, the entire connective Baltic energy infrastructure to CEN runs along the seabed and so is vulnerable to the sorts of incidents which occurred in 2023-24.
Operation Baltic Sentry is the result of this combination of vulnerability and real disruption. Its mission is to secure the critical infrastructure on the Baltic seabed. With no new incidents yet, the mission may perhaps be judged successful so far, but the pattern in the previous two years suggests that such incidents occur later in the year when energy consumption peaks during late autumn and winter. Therefore it is probably premature to judge mission success now.
Yet safeguarding critical infrastructure is not just a purpose, but also the means to other ends. First, it shifts useful alliance naval and air assets into the region: frigates and patrol ships, manned and unmanned airborne surveillance systems. These are assets which would have value in any regional crisis with Russia regardless of the on-going success or failure of Operation Baltic Sentry. Second, the operation has required training, exercises, and general military activity which improve readiness across involved military organizations. For example, the Finnish Navy has boasted that its original 17 hour response time has been decreased to less than one hour to get a surveillance drone aloft over any suspicious vessel within range. This both reflects and contributes to the need and ability of involved navies both to monitor the seas, particularly around the cables, every hour of every day and if necessary to send out one or more ships to provide presence near, or even to intercept, suspicious ship activity. Third, the mission demonstrates alliance solidarity and cohesion at a time when it is occasionally strained due to uncertain political currents within the alliance and some of its member states.
All of these features together then present a specific message to Moscow in case it considers military misadventure in the Baltic Sea region: the alliance intends to remain credible, both politically and militarily. In this way, therefore, a mission to protect critical energy infrastructure in the Baltic Sea region is also about so much more than just that, as critically important as that infrastructure is to the daily lives of these states’ inhabitants.
