Executive Summary
Between October 2023 and January 2025, four ships dragged anchors across Baltic seabed cables and pipelines: the Newnew Polar Bear over the Balticconnector; the Yi Peng 3 over the BCS East-West and C-Lion1 cables; the Eagle S over EstLink-2 plus four telecom cables; and the Vezhen over the Latvia-Sweden link. Two cases have since closed in court without a sabotage finding — the Helsinki District Court dismissed the Eagle S prosecution on 3 October 2025 for lack of jurisdiction under the Law of the Sea Convention, ruling the anchor loss a technical fault; Swedish prosecutors closed the Vezhen file in February and October 2025 as accident. The strategic implication survives the rulings: deniable grey-zone activity against undersea infrastructure is itself the threat, because the dependency creates leverage Russia exploits regardless of the verdict. Lithuania's NordBalt link to Sweden, the Klaipėda floating gas terminal moorings, the LitPol bridge, and the planned 2030 Harmony Link to Poland all run through seabed that no Lithuanian sensor watches. This is a gap Lithuania should close as a contributor to the alliance, not a beneficiary of it. The recommended next step is a defence-ministry feasibility study on a tiered underwater autonomous vehicle fleet — small harbour mine-clearance drones, medium long-endurance cable patrollers, and a small experimentation cell of larger vehicles — scoped to deliver capability inside the NATO Task Force X-Baltic Phase II framework Lithuania signed in February 2026. Reference costs anchor on Polish Navy Hugin procurement (about 10 million euros for three shipsets) and the September 2025 Australian Ghost Shark programme of record (1.7 billion Australian dollars for roughly 25 vehicles, implying a Lithuanian band of 30 to 65 million euros per large vehicle). Honest five-year envelope: 195 to 305 million euros. Final platform mix, vendor selection, and sequencing are Ministry of National Defence determinations.
The Problem
Lithuania's electricity, gas, and data run through seabed cables and pipelines no Lithuanian sensor watches. The 2022-2025 incident chain — Nord Stream September 2022 (cause disputed); Newnew Polar Bear over the Balticconnector pipeline October 2023; Yi Peng 3 over the BCS East-West and C-Lion1 cables November 2024; Eagle S over EstLink-2 and four telecom cables December 2024 (Helsinki District Court dismissed the prosecution on 3 October 2025 for lack of jurisdiction under the Law of the Sea Convention, ruled the anchor loss a technical fault); Vezhen over the Latvia-Sweden link January 2025 (Swedish prosecutors closed Feb and Oct 2025 as accident) — has produced a contested-attribution record, not a documented sabotage record. The strategic concern survives the rulings: Russia operates Kilo-class submarines from Kaliningrad and Baltiysk, the Belgorod special-mission submarine and Losharik deep-diving submersible, and the announced Argus-D large mine-laying underwater drone (H.I. Sutton, 2 January 2026, hisutton.com/Russia-XLUUV-Argus-D.html). A separate adversary template comes from the Iran 2026 war (28 February to 8 April 2026), in which the Iranian Revolutionary Guard mined the Strait of Hormuz from disguised fishing boats — the kind of attribution-deniable harbour mining a sovereign mine-clearance drone fleet at Klaipėda is built to detect.
Lithuania has zero sovereign underwater autonomous capability. The Lithuanian Naval Force (about 600 personnel, per the IISS Military Balance) operates four ex-UK Hunt-class mine countermeasures vessels with manned divers — adequate for harbour work, not for hundreds of kilometres of cable patrol. There is no procurement programme, no operator cadre, no sustainment chain, no domestic industry. Cable-damage detection relies on commercial outage reports and on allied frigates arriving 12 to 72 hours later. The southeastern Baltic — the sub-basin containing the NordBalt landing, the Klaipėda approach, and the future Harmony Link corridor — is the least-monitored Baltic sector. Lithuania has already signed the NATO Task Force X-Baltic Phase II Letter of Intent (February 2026), so the framework commitment exists; what is missing is the national fleet that would let Lithuania contribute to it rather than benefit from it.
Without action: A NordBalt cut on the existing pattern would cost an estimated 50 to 150 million euros per week of grid disruption plus 15 to 40 million in repair, against a five-year fleet envelope of 195 to 305 million. Lithuania remains a permanent victim-state of seabed damage with no detection, no attribution, and no deterrent signal. Macron's 2 March 2026 Île Longue speech named Germany, Poland, the Netherlands, Belgium, Greece, Sweden, and Denmark as French nuclear-doctrine partners; the Baltics were absent from the named list (not explicitly excluded, but read by Atlantic Council, ECFR, Chatham House, and CSIS as de-facto exclusion). The Treaty of Nancy (Poland-France bilateral, 9 May 2025) and its Gdansk follow-up of 20 April 2026 deepened the same circle without Lithuanian participation. Sovereign seabed capability is the kind of contribution that earns entry into the alliance circles forming in the 2027-2030 window.
Lithuanian Context
Baltic Sea conditions favour autonomous underwater vehicles: average depth 55m, maximum 459m, brackish water, semi-enclosed, and thousands of kilometres of mapped cable runs all sit inside Hugin and REMUS operational envelopes. The depth is not the constraint, endurance is. Klaipėda's existing port and naval-base infrastructure (drydock, lift, climate-controlled storage) supports sustainment without major new construction. Polish Navy Hugin operations next door and Swedish Saab industrial alignment provide regional training and supply chains. The single largest implementation question is the operator cadre: a fleet at the scale described above implies roughly 80 to 100 trained personnel, about 14 percent of current Lithuanian Naval Force headcount — a major reorganisation but well inside the realm of feasible, with explicit sourcing from existing mine-countermeasures crews, a new science-and-engineering conscription stream, and contractor field engineers from Kongsberg, Saab, and Anduril.