Submerged deep beneath the ocean, networks of undersea cables transmit over 95 percent of global Internet traffic, enabling high-speed communications and financial transactions that have become essential to contemporary life. Although these cables are generally highly reliable, even short disruptions in service can have negative impacts, and governments and companies are becoming increasingly concerned about cable protection. Roughly 150 to 200 cable faults occur each year, typically due to damage from ship anchors, natural disasters, current abrasion, or wildlife attacks.[1] In recent years, intentional damage to cables has also become more of a concern. For example, ships linked to China and Russia have been suspected of damaging cables near Taiwan and in the Baltic Sea, which has fueled fears that cable sabotage could be used as part of hybrid warfare, and espionage is also a potential threat.[2]

The US and Japan share interests in protecting undersea cable infrastructure for their own national prosperity and security, as well as to ensure the stability of the global economy on which they both depend. The two countries also play an important role in shaping the cable industry. For example, Japan’s NEC and US-based SubCom are two of the world’s top suppliers of undersea cables, and the “hyperscalers” Google, Meta, Microsoft, and Amazon have grown in importance as purchasers of cable capacity as well as investors in and builders of cable systems.[3] Therefore, the US and Japan have a valuable opportunity to work together to promote the resilience of undersea cable networks for mutual benefit. This article highlights several areas where US-Japan collaboration can make an important contribution and discusses some of the initiatives that are currently in progress.

First, the US and Japan can cooperate to increase resilience to disruption by expanding production and installation of undersea cables—both in terms of cables connected to their own countries and cables connected to other strategic locations. Many efforts are already underway in this area, but they will require long-term commitment in order to effectively bolster cable resilience. For example, Japan’s Ministry of Economy, Trade and Industry and Ministry of Internal Affairs and Communications have designated the cable industry as a national security priority, and they are looking to support capital investment to boost production and installation of cables.[4] The US and Japan have partnered with Australia to invest in the Palau Cable and East Micronesia Cable construction projects due to concerns about the vulnerability of Pacific Islands countries to communications disruptions and the potential security threats posed by Chinese companies building cables in the region.[5] The US and Japan have also worked with Australia and India as part of the Quad Partnership for Cable Connectivity and Resilience; as of September 2024, the Quad partners have committed over $140 million to cable construction in the Pacific.[6] In addition to supporting national, regional, and global resilience by constructing a robust network, sustained US-Japan commitment to cable construction initiatives will also benefit Japanese and American companies and other trusted providers.

Second, the US and Japan can coordinate to expand the production of ships for cable laying, maintenance, and repair. There is a global shortage of these essential ships; only around 60 ships operate worldwide to deal with over 600 active and planned cables, and the majority of these vessels are aging.[7] Moreover, some of these ships may not be operated by trusted partners. Investing in ship production will create commercial opportunities for the US and Japan that will enable them to more readily take on large-scale construction projects. It will also benefit their security by enabling faster maintenance and repair of damaged cables and by reducing risk of espionage.[8] Japanese ministries plan to subsidize investments in cable-laying ships, so some steps are already in progress.[9] Investing in cable ships is also consistent with the desire of the Trump administration to revitalize US shipbuilding.[10]

Third, the US and Japan can continue to work together to promote good governance and regulation of cables, along with other like-minded partners. In some cases, this will entail improving policies within individual countries. For example, US regulations for protection are not currently applied to all cables landing on its territory.[11] There are also issues related to harmonizing policies across countries. For example, many states have not adopted legislation that explicitly criminalizes intentional damage to cables within their internal waters.[12] Rules and penalties related to tampering and disrupting cable operation need to be strengthened. In addition, enforcement of existing regulations is an issue; the International Cable Protection Committee has noted that states are not sufficiently enforcing their existing obligations to protect cable infrastructure under the UN Convention on the Law of the Sea.[13] The US and Japan can play a leading role in setting standards for cable protection and enforcement along with other countries through the ICPC and other venues. This will help to ensure consistent best practices and to discourage destructive behavior.

Fourth, the US, Japan, and other countries can consult and coordinate on measures to more effectively protect cables from unintentional and intentional damage. Although it is impossible to patrol the approximately 1.48 million kilometers of undersea cables in service globally, additional measures may be possible in shallower waters near coasts where cables are more accessible and therefore more vulnerable. Many current strategies are defensive, such as covering cables to prevent detection or digging trenches to protect them from being damaged by anchors. Satellite imaging can also be used to monitor for ships operating near cable locations. In addition, newer technologies also come with potential benefits and risks for cable protection. For example, products such as Sensor Monitoring and Reliable Telecommunications (SMART) cables equipped with sensors can monitor ocean conditions and potentially provide information to improve network integrity; however, such technologies may also introduce cybersecurity risks. Similarly, some analysts have proposed that uncrewed underwater vehicles (UUVs) could be used to monitor and repair cables; however, they could also potentially be used to sabotage them.[14] As threats to cables evolve, the US and Japan must cooperate to share information and to stay on the cutting edge of new methods for monitoring and protection.

In summary, the US and Japan have clear incentives to protect the undersea cable network, and their existing strengths make them well positioned to bolster the resilience of this critical infrastructure. By collaborating with one another and with other countries, the US and Japan can ensure the reliability and security of global communication networks while also creating commercial opportunities for their respective companies in the cable industry and related sectors. Many initiatives are already in progress, but sustained commitment is necessary to genuinely strengthen cable resilience. Given the importance of undersea cables to the telecommunications and financial networks that support the global economy, the cost of not protecting these cables is simply too high to ignore.