WHAT CHANGED SINCE APRIL

The April edition of this briefing assessed undersea cables as a growing hybrid-warfare target. Five months later the picture is sharper in three places. In Europe the legal fight has started in earnest: Finnish prosecutors charged two officers of the cargo ship Fitburg in June, and on 27 August the Helsinki Court of Appeal ruled that Finland can try the officers of the tanker Eagle S for the Christmas 2024 cable cuts. In the Middle East, the war with Iran has created a second cable chokepoint in the Persian Gulf next to the existing risk in the Red Sea. And near Taiwan, a Chinese vessel damaged a Matsu cable on 30 March.

Governments are responding with money and legal tools rather than warships alone. The EU announced €347 million for cable security and repair in February, NATO's Baltic Sentry patrols continue, and Finland and Taiwan are prosecuting ship crews. The central problem has not changed: cutting a cable with an anchor is cheap, deniable and hard to prove as deliberate.

130 km
Anchor drag alleged in the Fitburg case
€347M
EU cable security funding announced in 2026
5
Cable segments under the Strait of Hormuz
20+
Cuts to Matsu cables in five years

WHY UNDERSEA CABLES MATTER

Around 99% of intercontinental internet and data traffic travels through fibre-optic cables on the seabed, not satellites. The same cables carry financial transactions, cloud services and government communications. Many also run alongside power cables and gas pipelines, as in the Baltic Sea. A single cable is usually not critical because traffic can be rerouted, but several cuts at once, or cuts to an island with few links, can slow or shut down connectivity for weeks. Repairs need specialised ships, which are scarce and cannot operate safely in war zones.

TIMELINE: 2023 TO SEPTEMBER 2026

THE BALTIC SEA: FROM SUSPICION TO THE COURTROOM

The Baltic has seen the most incidents: at least eleven cables damaged since late 2023, along with a gas pipeline, usually by ships dragging anchors across the seabed. Many of the ships involved were linked to Russian trade, including the "shadow fleet" of old tankers Moscow uses to export oil despite sanctions. Intelligence assessments are divided. Some US and European officials have said that several incidents were probably accidents caused by poorly maintained ships and inexperienced crews. Others see a pattern too consistent to be chance.

What changed in 2026 is that the cases are now being tested in court. In the Fitburg case, prosecutors allege the crew cut two telecom cables and tried to damage eight more by dragging a damaged anchor for at least 130 km before Finnish authorities stopped the ship. The defendants deny the charges and argue Finland has no jurisdiction because the damage happened in Estonia's exclusive economic zone.

That same jurisdiction question sank the first Eagle S trial in October 2025. The appeal court's August ruling reversed it, finding that the damage directly affected Finland and did not count as a maritime accident under international law, whose jurisdictional limits were written for collisions and similar accidents. The ruling can still be appealed to the Supreme Court until 26 October, and the three officers have already left Finland. If it stands, it will give Baltic states a clearer legal path to prosecute crews for damage outside their territorial waters.

THE GULF: WAR CREATES A SECOND CHOKEPOINT

The war with Iran has turned the Persian Gulf into a new risk zone for data as well as oil. According to industry reporting, there has been no confirmed deliberate attack on a cable, but the war has stopped work across the region:

On 9 May Iran said it would "impose fees on internet cables" in the Strait of Hormuz. The International Cable Protection Committee counts five active cable segments in the strait and says they carry less than 1% of global international bandwidth, so the global impact would be limited. The regional impact would not be: Gulf states rely on these links, and repair delays can turn small faults into long outages. Together with the Red Sea, where cuts in 2024 and 2025 slowed internet across the Middle East and South Asia, the region now has two conflict zones sitting on its main data routes.

TAIWAN: ISLANDS WITH TOO FEW LINKS

Taiwan's outlying islands are the clearest example of how cable damage can be used as pressure. Cables to the Matsu islands have been cut more than 20 times in five years; in February 2023 two cuts left residents with limited internet for weeks. In February 2025 the Chinese-crewed Hong Tai 58 dragged its anchor across the cable to Penghu inside a marked no-anchoring zone, and its captain was later sentenced to prison.

On 30 March 2026 the Taiwan–Matsu No. 3 cable was partly damaged while the Chinese vessel Hai Hong Gong 66 was removing a stranded Chinese fishing boat. Taiwanese authorities said they could not rule out a Chinese "grey-zone" operation, although the circumstances also fit an accident. Taipei has since tightened penalties for damaging cables and stepped up coast guard monitoring of ships near them. The wider context is covered in our Taiwan Strait briefing.

STRATEGIC ACTORS

Russia

Russia has the most developed capability to operate on the seabed, including the GUGI deep-sea research directorate and specialised submarines able to work at great depth. It also operates the shadow fleet whose ships appear repeatedly in Baltic incidents. No Baltic case has been proven in court to have been ordered by the Russian state, and Moscow denies involvement.

China

China is both a major cable builder and a suspected source of pressure. Chinese-crewed or Chinese-owned ships have been involved in incidents in the Baltic and around Taiwan. Beijing rejects the accusations and describes the Taiwan cases as accidents.

Non-state and regional actors

The Houthis in Yemen have threatened Red Sea shipping for two years and have been blamed for earlier cable damage, but they denied the September 2025 cuts. Iran's threat to charge fees on Hormuz cables shows that a regional power can also use the seabed as leverage.

THE RESPONSE: PATROLS, MONEY AND LAW

NATO launched Baltic Sentry in January 2025 to increase air, sea and drone surveillance, and the same model was used for Arctic Sentry in 2026 (see our Arctic briefing). The EU is focusing on repair and resilience. In February 2026 it announced €347 million: €60 million for repair equipment, €20 million for monitoring tools and €267 million in 2026–2027 for priority cable projects. It also published a Cable Security Toolbox and a list of Cable Projects of European Interest, and it plans a reserve of cable repair ships. A second €40 million call in June extended repair support from the Baltic to the Mediterranean and the Atlantic.

The legal response may prove most important. The Eagle S and Fitburg cases will show whether coastal states can prosecute ship crews for damage beyond their territorial waters. If they can, the cost of "accidental" anchor dragging will rise significantly.

INTELLIGENCE NOTE

"Seabed sabotage works because it sits in the gap between accident and attack. Patrols can shorten response times, and money can speed up repairs, but deterrence depends on attribution and punishment. The Finnish courts are now the front line of that effort, and their rulings over the coming months will matter more than any new patrol." — Based on Finnish court and prosecutor statements, European Commission, ICPC and industry reporting.

OUTLOOK: WHAT TO WATCH

The most likely trend is more incidents that stay deniable, rather than open attacks. The key risk is a coordinated series of cuts during a wider crisis — around Taiwan, in the Baltic or in the Gulf — when repair capacity is already stretched.

FREQUENTLY ASKED QUESTIONS

Why are undersea cables critical to global infrastructure?

Around 99% of intercontinental internet and data traffic travels through fibre-optic cables on the seabed. They carry financial transactions, cloud services and government communications. Several cuts at once, or cuts to islands with few links, can slow or shut down connectivity for weeks because repair ships are scarce.

Are undersea cables under threat in 2026?

Yes. In 2026 Finland charged the crew of the Fitburg over Baltic cable cuts, the war with Iran halted cable projects and repairs in the Persian Gulf, Iran threatened fees on cables in the Strait of Hormuz, and a cable to Taiwan's Matsu islands was damaged in March.

What is the Eagle S case?

The Eagle S is a tanker linked to Russia's shadow fleet that damaged the Estlink 2 power cable and four telecom cables between Finland and Estonia on 25 December 2024. A Helsinki court dismissed the case in October 2025 for lack of jurisdiction, but on 27 August 2026 the Court of Appeal ruled that Finland can try the officers.

Has Iran attacked undersea cables in the Strait of Hormuz?

No confirmed deliberate attack has been reported. On 9 May 2026 Iran said it would impose fees on internet cables in the Strait of Hormuz, which led cable company Alcatel Submarine Networks to pause regional repairs. Five cable segments pass through the strait, carrying less than 1% of global bandwidth but important regional traffic.

Which countries have the capability to target cable networks?

Russia has the most advanced seabed capability, including specialised submarines of its GUGI directorate. China operates large fleets of commercial and state vessels near key cables. But most recent damage has been caused by ordinary ships dragging anchors, which any state or group could use.

Where are the most vulnerable cable chokepoints?

The Red Sea and Suez route, the Strait of Hormuz and the Persian Gulf, the Baltic Sea, the Luzon Strait and the waters around Taiwan, and the Strait of Malacca. Islands with few connections, such as Matsu, are the most exposed.

How are governments protecting undersea cables?

NATO runs Baltic Sentry patrols with ships, aircraft and drones. The EU is spending €347 million on repair capacity, monitoring and new cables. Finland and Taiwan are prosecuting ship crews, and Taiwan has increased penalties and coast guard patrols around its cables.

AUTHOR

EDITOR · GEOPOLITICAL & MILITARY SYSTEMS

Kasim Kasimoglu is a geopolitical and military systems analyst focusing on conventional warfare, force posture, and nuclear deterrence. His analysis integrates open-source intelligence with structured military assessment frameworks, drawing on reporting from the Institute for the Study of War (ISW), the International Institute for Strategic Studies (IISS), and national defense ministries. His work centers on state-level conflicts across Europe and the Indo-Pacific, with an emphasis on operational dynamics and strategic balance.

Read more about the WarWatch editorial team on the About page.

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