Over 95% of international data, including financial transactions, military communications, and daily internet traffic, travel through submarine cables laid on the ocean floor (Wall & Morcos, 2021). Although this critical infrastructure remains largely invisible in public discourse, it is central to global security concerns. From daily communication to the global digital economy, submarine cables maintain the functionality of nearly every online action. As geopolitical tensions rise and cybersecurity threats grow, nations are reassessing the security, control, and strategic importance of this infrastructure.
Beyond supporting global connectivity, the strategic significance of submarine cables is most visible in regions where technological infrastructure intersects with geopolitical competition. The Indo-Pacific, which carries a substantial share of global internet traffic, has become a central area for the contestation. China’s increasing involvement in financing and constructing submarine cable projects has heightened concerns among the United States and its allies about foreign control, surveillance, and influence over critical infrastructure.
Within this context, Japan and the United States occupy significant positions. Japan’s reliance on stable digital connectivity is shaped by its island geography, its role as a regional financial hub, and its vulnerability to natural hazards that may threaten undersea routes. For Japan, disruptions to submarine cables would bring immediate economic and security consequences. The United States, in turn, integrates cable security into its broader Indo-Pacific strategy, linking infrastructure protection to alliance commitments and efforts to counterbalance China’s technological reach. Japan’s strategic collaboration with the United States on submarine cable infrastructure reflects a prominent effort to secure its digital sovereignty and reinforce regional stability in response to rising geopolitical threats. The collaboration between Japan and the United States on submarine cables has evolved not only into technical assets but also into tools of alliance-building.
The Strategic Stakes of Submarine Cables
Submarine cables are fiber-optic wires that lie along the seabed, designed to transmit data at high speeds and volumes across long distances. They are the backbone of the global digital economy. As of 2024, 559 cable systems and 1,636 landings are currently active or under construction, stretching nearly 1.5 million kilometers globally (Submarine Cable Map 2024, 2024). While often invisible in public discourse, these cables are vulnerable to both accidental and malicious damage (Runde et al., 2024). Common causes of disruption, including fishing trawlers, ship anchors, and natural events such as undersea earthquakes, contribute to over 100 reported cable faults annually (Niedbala & Berry, 2023). More concerning are intentional threats: cables can be tapped for espionage, which enables the theft of sensitive data, or sabotaged to cause widespread disruption (Ionut Arghire, 2023). A good illustration of submarine cables becoming a political concern is the Russian naval vessel Yantar, a deep-sea spy ship equipped with submersibles capable of tapping or severing submarine cables (Runde et al., 2024). Yantar has been repeatedly observed loitering near critical cable routes, prompting alarm among NATO members and defense officials from the U.S. and EU member states, who warned that Russia could target undersea communication cables as retaliation for alleged Western involvement in the blasts (Runde et al., 2024).
As recognition of their strategic importance grows, submarine cables have become central to the technological and geopolitical rivalries among global powers. Russian naval activity has raised concerns about the potential use of cable disruptions as a coercive tool, but the most sustained competition over infrastructure itself has emerged between the United States and China. This rivalry reflects broader struggles over digital dominance, technological standards, and control of critical global networks. China has advanced its influence through the “Digital Silk Road,” financing and constructing new undersea cables via state-backed firms such as HMN Tech (Runde et al., 2024). These projects not only extend China’s commercial reach but also raise concerns among other states about surveillance, dependency, and the strategic leverage Beijing could gain over global communications. The United States, in contrast, has actively aimed to restrict Chinese participation in major cable projects, citing national security risks, and has coordinated with allies to ensure that new routes are built by trusted partners. At the same time, commercial competition is deeply entangled with state interests. Chinese technology firms work in tandem with government initiatives, while U.S.-based corporations such as Google, Meta, and Amazon invest in private cable systems to secure faster and more autonomous data transfer between global data centers (Wallace, 2025). These private-sector projects, though commercially motivated, often align with U.S. strategic goals by reinforcing control over key routes and limiting opportunities for Chinese firms to expand their influence. The result is that submarine cables are no longer understood as neutral infrastructure but as strategic assets that underpin the global economy, international security, and digital sovereignty.
Japan’s Strategic Position in the Submarine Cable Landscape
Japan, located at a digital and geopolitical crossroads in East Asia, plays an important role in the global submarine cable network. Japan hosts 20 international cable landing stations, including 10 that connect to Asia and eight that reach the U.S. West Coast. (Gresh & Nakamura, 2023) Through systems such as the Australia–Japan Cable, the Japan–U.S. Cable Network, and SJC, Japan is deeply integrated into critical trans-Pacific and intra-Asian data routes.
The private sector also plays an important role in this strategic conflict. Japanese companies like NEC Corporation and KDDI are at the forefront of cable construction and management. NEC, along with its subsidiary OCC (Optical Cable Corporation), dominates over 40% of Southeast Asia’s submarine cable manufacturing market, second only to the U.S.-based SubCom (Gresh & Nakamura, 2023). Japan also maintains a robust capacity for cable maintenance and deployment through a fleet of specialized ships. This includes four to six cable-laying and repair vessels, operated by entities like NTT, KDDI, and the Japan Coast Guard, enabling rapid responses to disruptions and proactive infrastructure expansion (Gresh & Nakamura, 2023). A particularly strategic asset is the JS Muroto, a JMSDF deep-sea cable repair and surveillance vessel, which has participated in joint operations with the U.S. Navy, highlighting Japan’s defense cooperation with allies in securing critical infrastructure. Additionally, the Japanese government has launched a ¥50 billion (~USD 440 million) digital infrastructure initiative to decentralize landing points and bolster regional data resilience (Gresh & Nakamura, 2023). These combined efforts position Japan as both a technological hub and a strategic actor in shaping the security and governance of global submarine communications.
The U.S.-Japan Digital Security Alliance
The U.S.-Japan Digital Security Alliance represents a cornerstone of strategic cooperation between the two democracies, grounded in shared concerns over geopolitical and technological risks. As submarine cables become an essential component of both economic power and national security, Japan and the United States have stepped up efforts to align their policies, technologies, and partnerships around a common set of democratic values and trust frameworks.
One of the most prominent initiatives that reflects this collaboration is the Blue Dot Network (BDN), launched in 2019 by the U.S., Japan, and Australia (U.S Department of State, 2024). Although it does not directly financially support infrastructure, BDN establishes rigorous certification standards for transparency, labor, sustainability, and cybersecurity, shaping the norms of what constitutes “trusted” infrastructure development (The Blue Dot Network, a Global Collaboration Elevating Infrastructure Standards, 2025). In the new Trump administration, a notable announcement is the proposal to expand the DFC’s funding capacity from $60 billion to $250 billion, while also broadening its mandate to include investments in high-income countries (Furness, 2025). As the central supporter of the BDN, this increase in resources can signal a greater U.S. commitment and effort toward advancing the initiative.
Japan has actively promoted BDN as a strategic foreign-policy tool: under former Prime Minister Abe, it was envisioned as a “quality coalition” to promote infrastructure aligned with democratic norms, distinguishing it from China’s Belt and Road projects (Panda, 2020). Japan integrates BDN into existing policy frameworks such as the Expanded Partnership for Quality Infrastructure (EPQI) and the Free and Open Indo-Pacific (FOIP) strategy, both of which are formal government initiatives aimed at advancing high-standard, transparent infrastructure across the region (Panda, 2020). Japan’s role goes beyond endorsing BDN’s principles: institutions like the Japan Bank for International Cooperation (JBIC) work with U.S. and Australian counterparts to apply BDN’s certification standards in public–private infrastructure projects, which ensures that standards of transparency, sustainability, and labor are built into financing practices (Panda, 2020). These efforts, taken together, suggest that Japan uses BDN to extend its regional influence, promote infrastructure rooted in liberal values, and influence governance in critical sectors such as submarine cables. In this case, BDN standards function as technical and political baselines for digital connectivity projects, aligning them more with democratic partners.
Japan’s cybersecurity collaboration with the United States is also significantly reinforced through its participation in the Quadrilateral Security Dialogue (Quad), particularly the Quad Senior Cyber Group (QSCG) (The White House, 2023). This initiative, which includes Australia, India, the U.S., and Japan, aims to enhance coordination on cybersecurity standards and incident response across critical infrastructure sectors, including submarine cables, telecommunications systems, and energy networks (Fabiani, 2022). For Japan, this partnership fits into its broader strategy to address cyber and physical security risks around its maritime borders, while also indicating its dedication to upholding shared democratic values (Ministry of Foreign Affairs of Japan, 2023). In 2023, the Quad launched the Partnership for Cable Connectivity and Resilience, a landmark initiative to protect and expand submarine cable infrastructure throughout the Indo-Pacific (Department of the Prime Minister and Cabinet of Australia, 2024). As part of this effort, Japan has provided technical assistance and regulatory guidance to support secure cable landing operations in vulnerable island nations like Kiribati and Nauru (Yamaguchi, 2023). The initiative not only strengthens Japan’s bilateral ties with the U.S. but also positions Tokyo as a trusted regional actor in securing digital infrastructure. By working through multilateral forums like the Quad and focusing on practical cooperation in the submarine cable space, Japan amplifies its strategic influence while helping shape a resilient, rules-based digital environment in the Indo-Pacific.
Japan’s engagement in the Clean Network Initiative further reinforces its commitment to digital security. Launched in August 2020 by U.S. Secretary of State Mike Pompeo, the program aims to exclude “untrusted carriers” and vendors, such as those linked to authoritarian regimes, from global digital infrastructure, including submarine cables (U.S. Department of State, 2020) Although the initiative was short-lived and has since faded from public view, it marked an early U.S. attempt to build international structured standards for certifying reliable actors in digital infrastructure. In October 2020, Japan’s Foreign Minister Toshimitsu Motegi publicly endorsed the Clean Network’s expansion to submarine cable systems, aligning Tokyo’s infrastructure policies with U.S.-led trust frameworks, in which allied nations are considered “trusted” while geopolitical rivals, such as China, are excluded. (Press Conference by Foreign Minister MOTEGI Toshimitsu, 2020). Coupled with broader Japanese restrictions on Chinese telecom vendors such as Huawei, this approach underscores Tokyo’s commitment to democratic digital standards and enhances the strategic alignment of Japan and the U.S., framing their collaboration as both values-driven and security-focused (Schoff, 2020).
Vulnerabilities and Strategic Balancing
While the U.S.-Japan partnership on secure digital infrastructure demonstrates shared strategic ambitions, it is constrained by geopolitical risks and logistical vulnerabilities that complicate implementation and long-term resilience. Japan’s geographic proximity to China and North Korea places it on edge in an increasingly contested maritime region, which directly affects the U.S.-Japan relationship since Japan serves as a frontline hub for U.S. command, control, and digital connectivity in the Indo-Pacific. This strategic positioning brings risks to submarine cable infrastructure, which is critical for digital connectivity and military command. Recent reports, including those from the Asia Maritime Transparency Initiative, stated that some unusual movements of Russian and Chinese surveillance and civilian ships near Japan’s undersea cable routes have been noticed, raising concerns about the potential espionage or sabotage (Dzirhan Mahadzir, 2025; Runde et al., 2024). Also, geopolitical rivals such as China pose risks by slowing or denying permits for new cable routes in contested waters, such as the South China Sea (Goodman & Wayland, 2022). In response, U.S. authorities have already blocked subsea cable projects with Chinese landing points on national security grounds, such as the Pacific Light Cable Network (PLCN) to Hong Kong, while rerouting others through more trusted regions like the Philippines (Gross et al., 2023).
Beyond geopolitical concerns, technical and logistical limitations cause significant challenges for the U.S.-Japan submarine cable partnership. A 2024 CSIS report highlights that over 50% of cable faults result from human factors such as fishing gear and anchor damage (Goodman & Wayland, 2022). However, global repair capacity remains limited, with fewer than 100 cable repair vessels available worldwide (SAFETY4SEA Editor, 2025). China’s state-linked repair companies, such as SBSS, dominate the market regionally and have been accused of operating covertly and delaying operations in sensitive regions, including the South China Sea (Runde et al., 2024). To address the potential risk, the U.S. and Japan are pushing to diversify repair fleets and strengthen domestic cable-laying capabilities. Chinese firms, such as HMN Technologies, which are often 20–30% cheaper, threaten allied control over digital infrastructure (Runde et al., 2024). To remain competitive, allies should leverage development finance institutions, export credit agencies, and multilateral banks to support trusted vendors (Runde et al., 2024). Securing these systems is essential not only to counter sabotage and espionage but also to reduce dependence on authoritarian suppliers and ensure resilient, democratic digital dominance.
To manage such vulnerabilities, Japan has implemented regional resilience strategies such as the Yokohama Zone collaboration, a multinational agreement established in 1997 for the Pacific Ocean Cable Maintenance Zone. This arrangement coordinates emergency repairs through pre-positioned cable-laying and repair vessels stationed in Japan’s port of Yokohama. Under this framework, two standby ships equipped with remotely operated vehicles (ROVs) and spare parts remain available to rapidly service damaged cables across the Asia-Pacific region (Yokohama Zone, 2025). The Yokohama Zone enables participating nations to share maintenance costs, prioritize urgent repairs, and borrow assets during crises, enhancing redundancy across a fragile and interdependent infrastructure network. Japan’s leadership in this agreement underscores its dual role as both a regional coordinator and a frontline actor in securing critical undersea infrastructure (Yokohama Zone, 2025). These collaborations are crucial for reducing downtime, mitigating the risk of foreign sabotage, and reinforcing regional digital resilience in the face of mounting strategic pressure.
Implications
Submarine cables have become a critical topic in recent years, not only within the internet infrastructure world but also in global politics and strategic competition. These fragile yet vital systems enable global connectivity while reflecting a nation’s technological capabilities, geopolitical alignments, and strategic priorities. The collaboration between Japan and the U.S. on submarine cable infrastructure highlights a broader effort to strengthen alliances and secure critical digital assets in the face of rising cyber and physical threats. This partnership sends a clear message to the international community: working with trusted, technologically advanced partners is not just beneficial, but a strategic necessity. It also signals a long-term shift that the collaboration in digital infrastructure, particularly submarine cables, will become a cornerstone of international relations and security strategies in the years ahead.
As global reliance on digital infrastructure deepens, the strategic importance of submarine cables will only grow. The partnership between Japan and the United States reflects a proactive approach to securing critical technologies and reinforcing trusted international alliances. In a world where technological competition and geopolitical tensions increasingly overlap, such collaborations set a clue for how nations can jointly respond to emerging threats. Moving forward, building resilient, transparent, and secure digital networks will be essential not only for economic prosperity but also for safeguarding democratic values and international stability.
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