Ghosts of the Deep: China's AJX-002 XLUUV and the Geopolitics of Undersea Power

Ghosts of the Deep: China's AJX-002 XLUUV and the Geopolitics of Undersea Power
by Scott N. Romaniuk and Laszlo Csicsmann
Budapest, Hungary (SPX) Sep 11, 2025

China's unveiling of the AJX-002 eXtra Large Uncrewed Underwater Vehicle (XLUUV) at its September military parade in Beijing is more than just a flashy demonstration of hardware - it's a stark message that China is serious about redefining the underwater battlespace. At roughly 18 - 20 metres long and with a slim 1 - 1.5-metre diameter, the AJX-002 isn't just big - it's a platform designed to make its presence felt across the Taiwan Strait and beyond. Unlike previous smaller unmanned subs, the AJX-002 boasts cruciform rudders and quiet pumpjet propulsion, allowing it to slice through waters stealthily, while minimising acoustic detection. Its four lifting lugs hint at modular deployment capabilities, likely crane-assisted pier-side launches, making it both versatile and logistically nimble.

But the hardware is only half the story. The mission profile - primarily mine-laying - is deceptively simple on paper yet terrifying in strategic terms. Imagine a fleet of these autonomous submarines, weaving under the waves, dispersing mines or other payloads while human operators sit hundreds of kilometres away, monitoring their progress. Analysts speculate that their secondary roles could encompass reconnaissance, anti-submarine warfare, and even strike missions. The exact payload remains classified, but the modular design suggests it could carry torpedoes, mines, or other weaponised systems. This flexibility dramatically complicates traditional naval defence, turning the AJX-002 into a versatile tool for area denial and psychological warfare.

China isn't stopping there. The AJX-002 is just one part of a larger XLUUV programme that reportedly includes at least six distinct designs. During parade rehearsals, four AJX-002 units and two larger variants, such as the HSU-100, were observed. The HSU-100, with a greater diameter, twin masts, and X-form rudders, seems optimised for intelligence, surveillance, and reconnaissance tasks. By diversifying the XLUUV fleet, China is hedging its bets: some units focus on stealth and strike, others on ISR, giving the People's Liberation Army Navy (PLAN) an asymmetric edge in undersea warfare. This multipronged approach ensures that no single system is overexposed to detection or countermeasures, making the Chinese undersea fleet a more unpredictable adversary

Strategically, these drones are a game-changer. In the Taiwan Strait, their mine-laying capabilities could disrupt shipping lanes, threaten naval task forces, and create underwater denial zones.

Strategically, these drones are a game-changer. In the Taiwan Strait, their mine-laying capabilities could disrupt shipping lanes, threaten naval task forces, and create underwater denial zones. Beyond regional applications, they could be used to interfere with undersea cables, port infrastructure, or even civilian maritime traffic, adding a new layer to China's grey-zone operations. For adversaries, tracking these silent predators is a nightmare; traditional anti-submarine warfare tactics rely heavily on detecting sound, and a pumpjet-powered, autonomous vehicle significantly diminishes that advantage. The operational envelope of the AJX-002 extends both in range and endurance, granting China a persistent undersea presence without exposing human crews to risk.

The emergence of the AJX-002 also underscores a broader trend: autonomous systems are rapidly taking centre stage in modern warfare. Unlike crewed submarines, XLUUVs can operate longer, travel further, and undertake riskier missions without endangering personnel. These drones are essentially underwater "ghosts", capable of shaping conflict in ways conventional forces cannot easily counter. Their deployment changes not only tactical considerations but also the strategic calculus for regional actors, who must now contend with threats that are harder to predict and more difficult to neutralise.

The implications extend beyond the battlefield. Rival navies, particularly the U.S. and Australia, are now forced to accelerate their own unmanned undersea programmes. Australia's Ghost Shark project, for instance, can be seen as a direct response to China's ambitions, emphasising stealthy surveillance and strike potential. Similarly, the U.S. Navy has ramped up its XLUUV and autonomous undersea warfare programmes, recognising that the underwater domain is rapidly entering an era dominated by AI-driven platforms. In essence, the AJX-002 isn't just a technological marvel - it's a geopolitical signal, challenging regional actors to rethink maritime strategy in an era of autonomous warfare and demonstrating China's intent to dominate not just the surface, but the depths beneath it.

The AJX-002 is, in short, a glimpse into the future of naval conflict: modular, autonomous, and unflinchingly lethal. It's stealth meets strategy, intelligence fused with intimidation, and autonomy married to ambition. For anyone monitoring the Indo-Pacific, China's underwater drones are a wake-up call: the silent war beneath the waves has just begun, and the AJX-002 is leading the charge. Its presence reshapes maritime power dynamics, and the world is only beginning to grasp the implications of these ghostly sentinels prowling the deep.

+ Scott N. Romaniuk: Research Fellow, Centre for Contemporary Asia Studies, Corvinus Institute for Advanced Studies (CIAS), Corvinus University of Budapest, Hungary

+ Laszlo Csicsmann: Full Professor and Head of the Centre for Contemporary Asia Studies, Corvinus Institute for Advanced Studies (CIAS), Corvinus University of Budapest, Hungary; Senior Research Fellow, Hungarian Institute of International Affairs (HIIA)