The cables that carry nearly all of the world’s intercontinental data along the ocean floor have moved from being treated as a piece of background infrastructure to being recognized as a strategic asset whose vulnerability shapes the calculations of states and the resilience of the global economy. The shift in attention reflects both the indispensability of the cables and the growing recognition that they are exposed in ways that have not been adequately addressed.

A common misconception holds that the bulk of international internet traffic moves through satellites, when in fact only a small share does. The dominant medium is the fiber-optic cable, laid in great bundles across ocean basins, that links the world’s data centers and carries the financial transactions, communications, and content on which modern life depends. The cables are remarkable feats of engineering, but they are also relatively few in number along the most heavily used corridors, and their landing stations cluster in a small number of coastal sites where geography and history have concentrated them.

This concentration creates chokepoints whose disruption would impose costs out of proportion to the physical effort required to disrupt them. A cable can be severed by accident, by trawling, or by deliberate action, and the same vessel that might repair it serves as the only practical means of restoration. Repair fleets are small, repair times are measured in weeks rather than hours, and the queue of repairs has grown longer as cable counts have multiplied without proportional investment in the ships and crews that maintain them. The mismatch between the criticality of the asset and the capacity to fix it has become harder to ignore.

State actors have increasingly framed cable security as a national interest. Patrols by naval forces near important cable routes have become more visible, agreements among allies to share information about suspicious activity have expanded, and discussions about the manufacturing and ownership of cables and their supporting equipment have moved from the technical to the strategic. The recognition that a small number of firms produce the components and lay the cables, and that their nationality and relationships matter, has reshaped how procurement is approached for new routes deemed sensitive.

Incidents involving cable damage, whether accidental or otherwise, have demonstrated the consequences. Localized outages can cut financial centers off from counterparties, reduce communications capacity in islands and remote regions to a fraction of normal, and force traffic onto longer paths whose capacity may be insufficient. The economic costs accumulate quickly, and the difficulty of attributing damage to a specific cause complicates both the policy response and the deterrence of future incidents. Ambiguity in attribution is part of what makes cables attractive targets and difficult ones to defend.

Redundancy is the principal hedge, and the industry has pursued it through new routes that diversify away from concentrated corridors. The expansion of cable construction in recent years has added meaningful capacity along alternative paths, and the involvement of large content firms in financing and owning cables has changed the economics of who builds and where. Yet redundancy is uneven across regions, and the parts of the world that depend on a small number of cables for the entirety of their international connectivity remain vulnerable in ways that the most heavily connected regions are not.

Policymakers face the challenge of governing an asset that crosses national jurisdictions, that is built and operated by private firms across many countries, and that intersects with both commerce and security. Coordinating standards for protection, sharing intelligence about threats, building repair capacity, and managing the interaction between commercial decisions and national interests are all parts of an agenda that no single government can advance alone. The institutions for doing so are immature, and the pace at which they are developing lags the pace at which the strategic importance of the cables is growing.

The cables on the ocean floor will likely never carry the visibility of more obvious symbols of geopolitical contest, but the recognition that they constitute a critical and exposed piece of the international system is shaping policy, investment, and the quiet maneuvering of states. The infrastructure of the connected world is more concentrated and more vulnerable than the daily experience of its users would suggest, and the calculations now under way around its security will help determine the resilience of much that depends on it.