Over the March 22 weekend, it was reported that the China Ship Scientific Research Centre (CSSRC) and its affiliated State Key Laboratory of Deep-sea Manned Vehicles have developed a ship able to cut cable lines at depths of up to 4,000 meters (13,123 feet). Though subsea cable ships are outfitted with equipment to repair damaged or cut cables, the record depths to which this ship can go and the increasing tension in maritime areas with critical subsea infrastructure suggest that China has strengthened a tool in its arsenal, whether for intentionally cutting cables or supporting “marine resource development,” as alleged by Chinese scientists.
In the great power competition between the United States and the People’s Republic of China (PRC), subsea cables have emerged as critical theater, given that they are indispensable to international communications and are vulnerable to deniable intentional disruption; accidental cuts; surveillance, particularly at cable landing sites; and other risks. Regarding cable cuts, Taiwan has long accused China of deliberately cutting its cables through grey zone tactics. In response, China has argued that any cuts to Taiwan’s cables were due to maritime accidents, which are admittedly a common occurrence. While it is difficult to definitively establish whether such cuts were intentional, the PRC—by recently unveiling a new ship with the distinct purpose of cutting undersea cables—has laid bare that it regards sabotage and other intentional alteration of cables as just another coercive move in its playbook. Specifically, these actions signal that the PRC will likely further deploy cable cutting capabilities in the Taiwan Strait, the South China Sea, and beyond.
The 1.2 million kilometers of subsea fiber-optic cables are responsible for more than 99 percent of intercontinental data traffic. These cables push through terabits of information per second, compared to a gigabit of data per second transmitted by satellites. Subsea cables support nearly all aspects of business and everyday activity, constituting critical digital infrastructure upon which the world depends. Financial institutions, for example, transact an estimated $22 trillion per workday through these cable systems, and people worldwide rely on them to send and receive emails and stream movies.
Subsea cables lie directly on the seabed floor and are vulnerable to rough terrain, natural disasters such as volcanoes and earthquakes, accidents from dropped ship anchors, or intentional cuts. Most cuts are accidental, usually from fishing vessels or cargo ships that drop anchors without realizing what is beneath them. However, with questions surrounding the cable cuts late last year in the Baltic Sea and the revelation about the Chinese cable cutting ship, the United States and its partners and allies will need to intensify existing efforts to build resiliency and redundancy into the systems, and to quickly identify cable cuts and attribute them to the intentional actions of states in appropriate cases.
As part of CSIS’s ongoing research project on subsea cables, recent field visits to Ireland, Egypt, Japan, and Singapore reflected concerns about scenarios involving intentional sabotage. One or two cuts to cables can be dealt with, particularly if there are other cables that connect to countries or regions and internet traffic can be rerouted through other fiber-optic pathways. However, interviewees noted that multiple cable cuts, especially in an active conflict zone, would strain the limited cable repair ship capabilities and potentially knock countries, if not regions, offline for weeks or months. This scenario is mainly a concern of policymakers and government officials (most private sector entities are concerned with the ongoing issues on permitting and regulations that often stymie projects and hinder repairs). One real world example was an early 2023 cutting of two cables connecting Taiwan’s Matsu Island, preventing its 14,000 residents from using the internet. A Chinese fishing vessel and cargo ship were blamed for the cuts, though Taiwan officials stopped short of calling the cuts deliberate. Residents could not send texts, pay bills, operate businesses, or undertake e-commerce, among other disruptions. Policymakers worry about this being replicated on a much larger scale.
In addressing these concerns, it should be noted that the subsea cable industry—which is generally responsible for making decisions about when, where, and how to build new cables—is driven by commercial incentives, rather than national or international security imperatives. Approximately 98 percent of the world’s undersea cables are manufactured and installed by four private firms: SubCom (United States), Alcatel Submarine Networks (France), Nippon Electric Company (Japan), and HMN Technologies, (China, formerly known as Huawei Marine Networks Co., Ltd). Commercial undersea cables are typically owned by a single company or a consortium of companies that include telecommunication providers, undersea cable companies, content providers, and cloud computing service providers. Amazon, Google, Meta, and Microsoft now own or lease around half of all undersea bandwidth worldwide.
The commercial-driven approach to subsea cables has been an unmitigated boon for international connectivity, with significant increases in cable construction and investment for over a decade (though HMN’s fast-growing, state-subsidized market share suggests that the PRC is seeking to undermine market competition in favor of state-led domination). In responding to the challenge presented by the PRC (as well as Russia), policymakers should reaffirm the key role of the market in building and maintaining subsea cables, while ensuring that private stakeholders work closely with national security agencies and other government and intergovernmental organizations to collectively address concerns about the threat that the PRC and others present to the subsea cable ecosystem.
One area ripe for collaboration is determining how to build redundancy into the subsea cable infrastructure. Nearly all the stakeholders interviewed over the course of CSIS’s research agree that more cables need to be laid. Individual companies deserve tremendous credit for seeking to achieve resiliency for their own cable networks, and organizations such as the International Cable Protection Committee have played a key role in bringing industry stakeholders together to coordinate on resiliency. That said, there is scope for upping these efforts to coordinate, especially to ensure the overall resiliency of the trusted subsea cable ecosystem is accurately examined, and adjusting based on that information. In this regard, governments and industry can work together to assess and bolster total system resiliency.
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There are two schools of thought as to how to build in redundancy. One school proposes laying cables in a designated corridor to prevent accidental cuts from ships, making it easier to work with the fishing industry to identify areas that can be avoided in laying cables or for fishing, and creating a smaller and more defined area to patrol for ships that could accidentally or purposefully cut cables. The downside of this approach is that it concentrates several cables in one area, making it easier to cut many at once. The other school favors laying more cables, but not in a concentrated area. This prevents chokepoints or concentrated areas for cutting; however, it runs into the challenge of finding many more suitable locations while ensuring there is no disruption to fishing areas or an increase in accidental cuts.
Both schools agree on one point: more cables. As this thinking is primarily driven by commercial interests, the public sector and multilateral development banks and financing agencies should consider ways to finance landing stations for cables and the construction and laying of cables themselves, especially for emerging and developing countries looking to expand connectivity and increase their economic competitiveness. Laying more cables would not only provide more redundancy but would provide more opportunities for trusted vendors to build the infrastructure, earning goodwill and contributing to economic growth and good digital governance to these countries. Additionally, the way that permitting and licensing requirements are implemented can result in delays, particularly when permits are required before operations can start; excessive red tape creates additional risk of multiple cable failure.
China’s newest capabilities also highlight the need for greater cooperation among governments and the private sector to protect the subsea cable network. The ocean is vast and cannot be patrolled by one country. At the same time, more joint patrols among cable-connected countries, particularly in areas where there are chokepoints, active conflict, or in geostrategic waters, can provide added security for cable repair ships and potentially deter saboteurs. Surveillance satellites can also play a critical role in tracking ships that are near subsea cables and flagging suspicious activity such as loitering near cables in areas that have no commercial value. Other tools, such as supporting or financing the deployment of sensors on cables, should be explored, as they would help operators survey any issues around the cable (particularly after a natural disaster or accident) and identify the ship that intentionally or accidentally cut a cable. At the same time, understandable concerns about surveillance and national sovereignty should be thoughtfully addressed when such sensors are deployed near countries. Implementing tools such as satellites and sensing may require updates to multilateral treaties, as there is a need for new international norms for behavior in the age of great power competition.
It is difficult to overstate the urgency of finding and implementing solutions to address these challenges. Multiple cuts to a subsea cable system, whether to the trans-Pacific cables or in the Suez Canal, would lead to immediate and devastating economic and information security consequences. And the reveal of China’s cable cutting ship should silence any doubts regarding the threat of intentional cuts.
Thus, greater urgency on bolstering and protecting this indispensable component of digital infrastructure is needed, as are stronger efforts for coordination between the public and private sector to build resiliency and redundancy into the subsea cable system.
Erin Murphy is the deputy director for the Chair on India and Emerging Asia Economics and senior fellow of Emerging Asia Economics at the Center for Strategic and International Studies (CSIS). Matt Pearl is the director of the Strategic Technologies Program at CSIS.
