Silent Leviathans in Asia’s Deepening Undersea Rivalry

China’s march into autonomous undersea warfare is reshaping the Indo-Pacific and forcing India to respond in kind.

China is quietly transforming the ocean depths into a new theatre of strategic competition. Its rapid advances in unmanned and autonomous underwater vehicles (UUVs/AUVs) now extend to the development of so-called ‘extra-extra-large’ platforms - autonomous submarines longer than 40 metres, comparable in size to conventional diesel boats, yet unencumbered by human crews. Designed for long-endurance missions, these machines are intended to roam the Pacific, the Indian Ocean and, in theory, even the approaches to America’s west coast.

Operating without crews and often without clear attribution, such systems blur the line between surveillance and attack, peace and provocation. In contested waters, even their presence - detected or suspected - can impose caution, delay decision-making, and erode deterrence.

Steel Shadows

Intelligence assessments suggest that China is testing several of these XXLUUVs, including platforms such as the AJX-002, fitted with pump-jet propulsion and optimised for precise, low-noise operations. Freed from the constraints of life-support systems, such vessels can devote their internal volume to fuel, batteries, sensors and weapons. Ranges of more than 10,000 nautical miles are plausible, allowing them to loiter for weeks or months at a time.

Their mission set is expansive. They can lay mines, deploy smaller drones, conduct intelligence and surveillance, transport special-operations divers, or strike targets using torpedoes and missile systems launched from standard tubes. Communications can be maintained through satellites, buoys or long-range acoustic links, enabling remote supervision from shore or from surface vessels.

Past confrontations in the South China Sea, including territorial disputes with Vietnam, the Philippines, and Malaysia, highlight the strategic leverage that even a handful of advanced platforms can provide in contested waters.

Floating Docks

Recent trials around Hainan in the South China Sea underline the seriousness of the programme. Two new uncrewed submarines have reportedly been based near Sanya, China’s principal hub for nuclear submarines and aircraft carriers. Unlike earlier extra-large UUVs that were craned in and out of the water, the newest and biggest platforms are housed in dedicated floating docks. One such dock, Zhuan Yong Fu Chuan Wu 001 (built as recently as 2024) can sail to sea, deploy or recover UUVs, and shield them from prying eyes in congested ports.

The infrastructure supporting these systems is as telling as the platforms themselves. Purpose-built floating docks signal that China is planning for routine, sustained operations of autonomous submarines, not sporadic trials. This suggests a doctrinal shift in which unmanned systems are expected to operate alongside, and eventually ahead of, crewed naval assets.

By easing handling and reducing exposure during launch and recovery, these docks make routine operations of giant autonomous submarines far more practical. They also hint at an ambition to integrate such systems into regular naval deployments rather than treat them as experimental curiosities.

The strategic implications are unsettling. Low-risk, high-endurance undersea platforms could complicate American and allied naval dominance in the Pacific, threaten shipping lanes, and add a new layer of uncertainty to the Indian Ocean. An accelerated undersea arms race looks increasingly inevitable.

For regional navies, the challenge lies in detection rather than destruction. Autonomous submarines are quieter, harder to track, and politically less escalatory to deploy than manned vessels. Their proliferation could therefore lower the threshold for undersea competition, even as it raises the risks of miscalculation.

India is not standing still. Confronted by China’s expanding naval footprint and by Chinese-enabled Pakistani capabilities, the Indian Navy has pushed ahead with its own unmanned-systems agenda. In line with its broader Aatmanirbhar Bharat doctrine, the emphasis has shifted from imported solutions to indigenous design and production.

A flagship programme launched in 2024 aims to field a dozen extra-large UUVs for intelligence, surveillance and reconnaissance, anti-submarine warfare and mine countermeasures, with prototypes expected within two to three years. The Defence Research and Development Organisation is also working on AI-driven underwater drone swarms and man-portable autonomous vehicles for mine clearance. Private firms, notably Larsen & Toubro, have expanded their role in meeting these requirements.

Alongside unmanned platforms, the navy is strengthening its broader undersea defences: commissioning Arnala-class shallow-water anti-submarine craft, fitting frontline ships with the Mareech advanced torpedo-defence system, and partnering with firms such as Sagar Defence Engineering on autonomous surface vessels and maritime robotics. A three-layered approach to maritime domain awareness - air, surface and underwater - is steadily taking shape.

Yet gaps remain. Critical sensors, subsystems and materials are still imported, leaving India dependent on foreign suppliers in some of the most sensitive technologies.

India’s task is thus not only technological but institutional. Integrating unmanned systems into fleet operations, doctrine and command structures will require a cultural shift within a navy long oriented towards crewed platforms. Closing those gaps will be essential if India is to counter China’s silent leviathans on equal terms.

(The author is a retired naval aviation officer and defence and geopolitical analyst. Views personal.)