🛰️ Taiwan Gray Zone & Submarine Cable Monitor

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Taiwan's Submarine Cable Landscape

Article Series 03 • Taiwan • Cable Infrastructure • Outer Island Vulnerability

SERIES → 01 Submarine Cable 02 AIS 03 Taiwan Status 04 Threats 05 Enforcement 06 Methodology
In February 2023, residents of Matsu woke up to find the internet was gone.

At first it seemed like a routine outage. Then the confirmation came, and it was alarming: on February 2nd, one cable was severed by a Chinese fishing vessel. Less than a week later, on February 8th, the second cable was cut too. Matsu — Taiwan's frontline island in the Taiwan Strait — lost both its submarine cables in 6 days.

Repair time? Nearly 50 days.
14
international submarine cables
10+
domestic cables (outer islands)
50 days
days to repair 2023 Matsu outage
2
cables total for Matsu's connectivity

Taiwan's Strategic Position and Cable Density

Taiwan sits at the crossroads of Asia-Pacific submarine cables. Cables running from Japan and South Korea southward to Southeast Asia and Australia, as well as transpacific trunk routes to the Americas, must skirt or pass through Taiwan's surrounding waters. The Taiwan Strait averages only about 60 meters in depth — shallow water that makes cables far more vulnerable to fishing activity and anchors.

Taiwan's main island currently has 14 international submarine cables landing at stations in Bali (New Taipei), Toucheng, Tainan, and Kaohsiung, connecting to the US, Japan, Hong Kong, the Philippines, Guam, and beyond. These cables are the physical backbone of Taiwan's external communications, financial transactions, and semiconductor order flows.

Major International Cables (Selected)
TPE (Trans-Pacific Express)
Taiwan ↔ Japan ↔ Korea ↔ USA
INTL
APCN-2
Taiwan ↔ Japan ↔ Korea ↔ Hong Kong ↔ SE Asia
INTL
TAW-US
Taiwan ↔ USA ↔ Guam
INTL
PCCS (Matsu)
Taiwan main island ↔ Matsu
DOM
MATSU-T (Matsu)
Taiwan main island ↔ Matsu
DOM
Kinmen Cable
Taiwan main island ↔ Kinmen
DOM

Outer Islands: The Most Vulnerable Links

Taiwan's main island has 14 international cables providing redundancy — if a few are cut simultaneously, others can absorb the traffic. But the outer islands face a very different situation.

⚠️ Matsu Islands
Matsu lies in the northern Taiwan Strait, only 10 km from China's Fujian coast — Taiwan's most frontline outer island. The entire archipelago depends on just 2 submarine cables (PCCS and MATSU-T) to connect with Taiwan's main island.

In February 2023, both cables were severed by Chinese fishing vessels within 6 days. Internet connectivity for Matsu's 14,000 residents was completely cut, with only extremely limited microwave communications remaining. Chunghwa Telecom activated emergency Starlink service as a temporary workaround, but bandwidth was severely insufficient. Repairs took approximately 50 days.
⚠️ Kinmen County
Kinmen lies in the southern Taiwan Strait, 10 km from China's Xiamen. It currently has 1 main cable plus 1 backup. While slightly better than Matsu, if both are simultaneously cut, Kinmen would face the same communication isolation.
🟡 Penghu County
The Penghu archipelago is closer to Taiwan's main island and has relatively more cable connections, giving it better resilience than Matsu or Kinmen — though still a weak point in Taiwan's outer island connectivity.

Break Trends: The Numbers Tell a Story

Submarine cable damage is a global norm — roughly 100–200 incidents per year worldwide, mostly from fishing and anchors. But Taiwan's unique geopolitical environment means break frequency far exceeds what geography alone would predict.

The Repair Challenge: More Than Just Waiting

Submarine cable repair is an extraordinarily specialized, time-consuming, and expensive undertaking. There are only about 60 dedicated cable repair ships in the world, distributed across the oceans, often requiring days just to reach the incident site.

What Does Repairing a Cable Require?
  • Deploy a dedicated cable repair ship (daily charter costs tens of thousands of dollars)
  • Precisely locate the break on the seabed (using Time Domain Reflectometry and ROV submersibles)
  • Raise the cable to the surface (extremely difficult in deep water)
  • Splice fiber optics in a specialized joint box
  • Return the repaired cable to the seabed and test signal quality
The full process typically takes 14–60 days depending on depth and damage extent. The 2023 Matsu outage took about 50 days to repair.

More challenging still: if multiple cables are simultaneously damaged (as in the 2006 Hengchun earthquake), the limited pool of repair ships must queue — wait times can stretch to months. This is precisely the maximum-damage scenario of a gray zone attack targeting multiple cables at once.

Government Response: Resilience-Building Efforts

Following the 2023 Matsu incident, Taiwan's government has moved more actively to address submarine cable vulnerability. Measures taken or planned include:

The fundamental problem: Even with a third cable installed, as long as the enforcement gap and flag-state jurisdiction loophole remain unresolved, deliberate saboteurs can repeat the same tactics. Hardware redundancy reduces the impact of any single incident, but cannot prevent the hostile behavior itself. This is the core issue explored in depth in Article 05: Enforcement Framework and Challenges.

The International Cables Landing in Taiwan — and Its "Landing Stations"

Taiwan's external connectivity is not spread evenly; it is highly concentrated in a handful of landing stations, where international cables come ashore and connect to the terrestrial backbone. Public records show Taiwan's main landing stations clustered around Toucheng and Tamsui in the north and Fangshan in the south.

Several major international cable systems meet here, linking Taiwan to Japan, Hong Kong, Southeast Asia, and across the Pacific. The catch: when landing stations and cable routes sit geographically close together, an event at a single site or in a single patch of sea can affect multiple cables at once.

This geographic concentration is two sides of one coin — efficiency and fragility. It makes construction and operations more efficient, but it also means a few critical nodes carry a disproportionate share of the risk — and when those waters are also busy fishing grounds and shipping lanes, separating "accident" from "intent" becomes harder still.

The outer islands are even more exposed: the cables serving Matsu, Kinmen and other offshore islands are few to begin with, with little redundant routing. Once damaged, local external communications may rely for a long time on microwave or satellite backup until repair — at a heavy cost in bandwidth and stability.

FAQ

Why was the Matsu internet outage so severe?
Matsu depends on just 2 submarine cables to the main island. In February 2023 both were cut by Chinese vessels within 6 days, leaving 14,000 residents offline for about 50 days.
How long does it take to repair a cut cable?
Typically 14–60 days depending on depth and damage. The 2023 Matsu repair took about 50 days, since only roughly 60 specialized cable repair ships exist worldwide and they often queue.
Is Taiwan's cable break frequency normal?
Globally there are ~100–200 breaks a year, but Taiwan's waters see a disproportionate share — 12 incidents in 2023, and 4 in just January–February 2025.
How many international and domestic cables does Taiwan have?
Taiwan's main island has 14 international submarine cables and about 10 domestic cables connecting outer islands like Matsu, Kinmen, and Penghu.
← 02 AIS Tracking Next: Threats to Submarine Cables →

Sources

The concepts on this page can be verified against these public, authoritative sources:

This page is for research and education; detection signals are leads to investigate, not legal or factual findings. See the methodology.

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