What Happens If the Undersea Internet Cables Are Cut?
The hidden network beneath the ocean, why one broken cable usually changes very little, and what happens when several routes fail at once
In September 2026, undersea cables near Svalbard appeared in the news for an uncomfortable reason.
Reuters reported that NATO allies had disrupted what Western officials described as a Russian operation involving deep-sea equipment near critical fiber-optic infrastructure linking Svalbard with mainland Norway. According to those officials, the activity involved Russia's GUGI deep-sea organization and appeared intended to test or rehearse capabilities that could be used against undersea infrastructure.
No cable was cut.
No Internet outage followed.
The Reuters report was based on Western intelligence assessments, and Russia has denied conducting sabotage operations against NATO countries.
But the story raises a much larger question.
What would actually happen if somebody did cut the cables?
Could a ship, submarine, natural disaster, or hostile state simply sever a few lines on the seabed and switch off the Internet?
The reassuring answer is no.
At least, not by cutting one.
And that is where the subject becomes much more interesting.
The Internet Is Far More Physical Than It Feels
We tend to experience the Internet as something almost weightless.
Your phone connects through radio waves. The laptop connects through Wi-Fi. Files disappear into "the cloud." A video arrives from another continent without anybody thinking very hard about how it crossed an ocean.
Somewhere underneath all of that wireless convenience is an enormous physical network.
More than 99 percent of international data traffic travels through submarine telecommunications cables, according to the International Telecommunication Union. The global network consists of hundreds of cable systems stretching across the world's oceans.
These are not simply ordinary electrical cables dropped into the sea.
Inside are strands of optical fiber carrying data as pulses of light. Long-distance systems include repeaters along the route to maintain the signal, with electrical power supplied from the cable landing stations at either end. Protective layers surround the working core, with heavier protection generally used where cables are more exposed to anchors, fishing gear and other hazards.
Then the cable reaches land.
From there, the data continues through terrestrial fiber networks, exchange points, data centers and the other infrastructure that makes the Internet appear effortless.
The ocean is therefore not something the Internet somehow jumps over.
The Internet crosses it.
Mostly through glass fibers lying on or beneath the seabed.
Cable Breaks Are Surprisingly Normal
This is where the picture becomes less alarming.
Submarine cables break all the time.
The International Cable Protection Committee reports roughly 150 to 200 submarine telecommunications cable faults worldwide each year. Around 70 to 80 percent are caused by accidental human activity, particularly commercial fishing and ships' anchors. Natural hazards, abrasion, equipment failure and other causes account for much of the rest.
So when a submarine cable fails somewhere in the world, sabotage should not be the automatic assumption.
Often someone dragged an anchor where they should not have.
A trawler caught something it would have been much better off leaving alone.
A submarine landslide moved across the seabed.
A component failed.
In most cases, you never hear about it.
That is not because the cable was unimportant.
It is because the network expected something to break.
So Why Doesn't the Internet Go Down?
Imagine driving between two large cities.
There is a motorway between them, but it is not the only possible road.
One morning the motorway closes.
Your navigation system sends you somewhere else. The trip may take longer. Other roads become busier. But unless you happen to be caught near the closure, you may barely notice what happened.
Internet routing works on a vastly more complicated scale, but the basic idea is useful.
A major network operator does not normally depend on one physical cable between two continents. There are different cable systems, different landing countries, different network operators and terrestrial routes connecting them.
When one route disappears, traffic can be moved elsewhere.
The physical cable can therefore be completely dead while the service it was carrying remains available.
That is an important distinction.
A cable failure is not necessarily an Internet failure.
In a well-connected part of the world, losing one cable may produce no visible effect at all for an ordinary user.
Some packets simply take another road.
The Trouble Begins When the Alternatives Disappear
Now close another road.
And another.
Traffic can still move, but the surviving routes are doing more work.
This is where redundancy stops being an abstract engineering word and starts becoming the entire story.
Every surviving fiber route has capacity.
If enough traffic is forced away from damaged systems, some alternative paths may become congested. Data may travel farther geographically. Latency can increase. Network operators may need to rebalance traffic. Some services may slow down while others continue normally.
And the effects will not necessarily appear evenly.
One customer may notice almost nothing.
Another may lose access to a particular service.
Another country or region may suffer a substantial reduction in international connectivity.
The important question is therefore not simply:
How many cables broke?
It is:
How much genuinely independent capacity remains?
Ten cables following broadly similar geography do not necessarily provide the same resilience as ten systems using genuinely different routes and landing regions.
That problem is now receiving serious international attention. The ITU's 2026 submarine cable resilience report identifies geographical concentration and dependence on small numbers of cable systems as major vulnerabilities, especially for smaller and more isolated countries. Its recommendations include greater route diversity and infrastructure redundancy.
Tonga: What Happens When There Is No Other Road
Tonga demonstrated the other extreme in January 2022.
The eruption of the Hunga Tonga-Hunga Ha'apai volcano and the resulting tsunami damaged the country's submarine cable.
For Tonga, this was not one route among many.
It was the country's only international submarine cable connection.
The result was severe international communications disruption. Emergency satellite connectivity was established for government agencies and essential services, but normal Internet access could not simply be transferred wholesale into space.
Full international fiber connectivity was restored 38 days later.
Tonga is obviously very different from Western Europe.
That is precisely why it is useful.
It demonstrates that digital isolation is possible.
The determining factor was not whether fiber-optic cables are inherently fragile. It was that there was no equivalent fiber route around the failure.
The network had reached the edge of its options.
Svalbard: Two Cables Do Not Make Europe
Svalbard offers a case much closer to home.
The archipelago is connected to mainland Norway by two submarine fiber-optic cables. They support ordinary communications on Svalbard, but also important infrastructure including the Svalbard Satellite Station and traffic management at Svalbard Airport.
One of those cables suffered an outage in 2022 and was later repaired.
Norwegian authorities have been unusually clear about the underlying vulnerability.
The government has stated that redundancy in telecommunications to Svalbard remains very limited and that existing and planned satellite systems would not provide enough capacity to meet Svalbard's needs during a prolonged failure of the present submarine fiber connection.
That is an important point.
Svalbard has more than one cable.
But that does not give it the same kind of connectivity enjoyed by mainland Europe, where international traffic can move through many different countries, terrestrial networks and submarine systems.
Norway is now establishing a new state-controlled submarine fiber connection involving the mainland, Jan Mayen and Svalbard, planned to become operational in 2028. Work is already underway.
So when the recent Russian activity near Svalbard reached the news, it attracted attention for a reason.
The infrastructure matters.
But Svalbard also shows why simply counting cables tells only part of the story.
Could Someone Cut North America Off From Europe?
This is where the dramatic version of the story begins to struggle.
Look at a modern submarine cable map of the North Atlantic and Western Europe and you do not see one neat line connecting America with Europe.
You see a network.
Multiple systems cross the Atlantic. They reach different parts of Europe. Ireland and the United Kingdom are important. France has major connections. Routes continue toward Scandinavia and continental Europe. Terrestrial fiber then gives network operators additional ways to move traffic between countries and onward to users.
TeleGeography's current submarine cable map shows hundreds of operational and planned systems globally and a dense concentration around Europe and the North Atlantic.
Cutting one transatlantic cable therefore does not cut America off from Europe.
Cutting several would not necessarily do it either.
Traffic can be rerouted through systems landing hundreds or thousands of kilometers away and then carried across land.
That does not make the network invulnerable.
It changes what a serious disruption would look like.
An attacker would not necessarily need to make communication impossible to cause problems.
Reducing available capacity at the wrong moment could be enough to create congestion, force rerouting, make some services unreliable and place additional pressure on surviving infrastructure.
NATO itself says approximately 95 percent of transatlantic Internet traffic, including military communications, is carried by undersea fiber-optic networks, most of them owned and operated by private companies.
That does not mean NATO would suddenly become unable to communicate if several commercial cables failed.
It does mean civilian digital infrastructure forms part of the environment in which modern governments and militaries operate.
There is no obvious Internet off-switch sitting somewhere on the floor of the Atlantic.
There is, however, a lot of infrastructure that becomes increasingly important as alternatives disappear.
Five Bars, but Nothing Useful Happens
Suppose the disruption becomes serious.
You pick up your phone.
Five bars.
Excellent.
Then nothing works.
That is entirely possible because the connection between your phone and the cellular tower is only one part of the journey.
The local mobile network may still be operating perfectly well.
But the application you are opening may depend on a server somewhere else.
Your account authentication may happen in another country.
A database may be hosted in a foreign cloud region.
The payment service may depend on an international network.
The website may call several external services before it can even load properly.
The physical infrastructure immediately around you can therefore remain alive while parts of your digital life become unreachable.
It would probably be messy rather than absolute.
One service works.
Another does not.
A website loads but cannot process your login.
A messaging app works intermittently.
Domestic websites remain reachable while overseas services time out.
People would quite reasonably stare at the signal indicator on the phone and wonder why five perfectly healthy bars had become decorative.
This is one of the odd characteristics of modern infrastructure.
What you can see working is not necessarily the part that failed.
Banking, Payments and the Cloud
Financial systems would create the same problem.
It would be misleading to say that cutting submarine cables would simply make credit cards stop working.
Modern banking systems contain extensive redundancy, and domestic systems can continue functioning even when some international connectivity is impaired.
But banking is also deeply networked.
Payment processors, card networks, cloud platforms, fraud systems, corporate data centers, market connections and authentication services can cross national borders.
A severe loss of international connectivity could therefore produce very uneven results.
One payment still clears.
Another fails.
Online banking works for one customer but cannot reach a service needed for another transaction.
A business remains connected to its Norwegian office but loses access to a cloud application hosted elsewhere.
Logistics systems encounter the same problem.
A warehouse does not need to be physically damaged to become inefficient. It only needs to lose access to the systems telling it what is arriving, where it belongs, who ordered it and where it should go next.
The ITU specifically identifies finance, government services, cloud services and other essential activities among the systems dependent on submarine connectivity.
Again, the likely result is not everything stopping at once.
It is systems becoming patchy.
And patchy systems are difficult because people continue trying to use them.
Can't Satellites Just Take Over?
This is usually the next question.
We have Starlink.
We have communications satellites.
We have military satellite systems.
Surely we no longer need glass fibers sitting on the ocean floor?
Satellites can help enormously.
Tonga used satellite connectivity to restore essential government and emergency communications while its cable was being repaired.
NATO is also funding a project called HEIST, Hybrid Space/Submarine Architecture Ensuring Infosec of Telecommunications, which is studying ways to reroute data through satellite systems when submarine cables are disrupted.
That tells us something important about how resilience is actually being approached.
The answer is not fiber or satellite.
It is fiber and satellite.
Satellite systems offer another path, which is exactly what redundancy requires.
But they cannot automatically absorb the enormous volume of international traffic normally carried by submarine fiber networks.
Norway has already reached that conclusion for Svalbard. Its government explicitly says available and planned satellite communications would not provide sufficient capacity during a prolonged failure of the submarine fiber connection.
Satellite can preserve communications.
It does not make the cables irrelevant.
What If the Cuts Were Deliberate?
This is where an engineering problem becomes a security problem.
The broad locations of submarine cables are not secret.
In many areas they are deliberately shown on nautical charts because ships need to know where they are.
Fishing vessels should not drag bottom gear through them.
Ships should not drop anchors onto them.
The International Cable Protection Committee has argued strongly that cables should continue to be charted for exactly this reason. It also points out that removing cables from public charts would provide little protection against a sophisticated adversary with other means of finding them.
That makes sense from a maritime perspective.
Hiding a hazard from every fisherman and shipmaster on the assumption that a state intelligence service will then be unable to locate it would be an unusual security strategy.
A capable state actor would also have access to hydrographic data, intelligence, surveillance and specialist naval capabilities far beyond an ordinary public map.
But the same network logic still applies.
Against a highly connected region, one cut has limited effect.
The security concern is the coordinated loss of several genuinely independent communications routes.
We do not need to identify particular cables, landing stations or vulnerable points to understand the problem.
The network does that for us.
Remove one route and traffic moves.
Remove another and the remaining routes work harder.
Keep removing independent alternatives and eventually redundancy becomes congestion, reduced capacity or isolation.
That is the scenario governments are increasingly preparing for.
Finland, for example, conducted a major maritime exercise in September 2026 involving the coast guard, police and armed forces practicing how to respond to suspected attacks on underwater infrastructure. Finnish officials emphasized that accidental anchor damage remains common, but that authorities also have to prepare for deliberate sabotage.
The concern is real.
That does not mean every broken cable is sabotage.
Most are not.
Could Communications Be Targeted Before a War?
Yes, in principle.
Disrupting an opponent's communications at the opening of a conflict is hardly a new military idea.
There is also a very recent precedent.
On February 24, 2022, a cyberattack struck Viasat's KA-SAT satellite communications network approximately one hour before Russia launched its full-scale invasion of Ukraine.
The United Kingdom's National Cyber Security Centre assessed that Russia was almost certainly responsible. The European Union formally attributed the attack to Russia and said it facilitated the military aggression. Ukrainian military communications were believed to be the primary target, but the effects spread beyond Ukraine and disrupted other users in Europe.
That does not prove Russia plans to cut North Atlantic submarine cables before a future conflict with NATO.
There is no public evidence establishing such a plan.
What it does establish is the logic.
Communications infrastructure can be targeted immediately before conventional military operations begin.
Western governments also say Russia possesses specialist deep-sea capabilities relevant to undersea infrastructure, which is why Russian activity around submarine cables is watched closely.
The September 2026 Svalbard incident therefore matters without needing to turn it into something it was not.
No cable was cut.
No attack on NATO occurred.
But the capability being discussed is real enough that governments are spending money, deploying ships, conducting exercises and building additional infrastructure to reduce the consequences if cables are damaged deliberately or accidentally.
The Real Story Is Redundancy
There are two easy ways to get this subject wrong.
One is to assume submarine cables are so vulnerable that a few cuts could instantly switch off the modern world.
The other is to look at the enormous global cable network and decide the problem has been engineered away.
Neither is particularly useful.
The cable network is remarkably resilient.
It survives failures every week.
Most of us never notice because operators reroute traffic, alternative systems absorb the load and repair ships eventually restore the broken link.
That is an impressive achievement.
But redundancy only exists while an independent alternative remains available.
That is why the current international effort is focused not simply on stronger cables, but on route diversity, alternative infrastructure, faster repairs, satellite backup and better coordination between governments and private operators.
A system does not have to be indestructible to be resilient.
It has to continue doing its job after something breaks.
That distinction appears repeatedly when you start looking closely at the infrastructure around us.
Power grids.
Water systems.
Navigation.
Food distribution.
Communications.
Most work so reliably that we stop seeing the machinery underneath them.
Until something stops answering.
Why This Belongs in SOLSTORM
The Solstorm Saga begins with failures in systems people normally take for granted.
Navigation becomes uncertain.
Communications disappear.
Power stops arriving.
The characters do not suddenly enter a world without technology. They enter a world where the networks connecting that technology no longer behave as expected.
Undersea cables are another version of the same problem.
They are normally invisible.
They cross oceans far beneath ordinary life, carrying messages, banking data, business traffic, government communications, cloud services and the millions of small digital interactions we now perform without thinking about them.
Most of the time, one can break and almost nobody notices.
That may be the most impressive thing about the network.
It may also be the most important thing to understand about its vulnerability.
The danger does not begin when one cable fails.
It begins when there is no longer another road.
ITU - Submarine Cable Resilience https://www.itu.int/digital-resilience/submarine-cables/
International Cable Protection Committee - Cable faults and causes https://www.iscpc.org/news/media-enquiries/
International Cable Protection Committee - Why cable routes are charted https://www.iscpc.org/publications/icpc-viewpoints/charting-submarine-cables-is-critical-for-maritime-safety-and-infrastructure-protection/
Norwegian Government - Svalbard communications infrastructure https://www.regjeringen.no/en/documents/meld.-st.-26-20232024/id3041130/?ch=4
Reuters - September 2026 Svalbard undersea cable story https://www.reuters.com/world/europe/nato-allies-foil-russian-subsea-cable-sabotage-plot-2026-09-10/
UK Government - Viasat cyberattack before the invasion of Ukraine https://www.gov.uk/government/news/russia-behind-cyber-attack-with-europe-wide-impact-an-hour-before-ukraine-invasion
