Deploy a large number of small drones to search close to the sea
In response to the rapid expansion of China's submarine combat capabilities, Japan is planning to build a new anti-submarine surveillance network using a large number of small drones. Nihon Keizai Shimbun reported that the Ministry of Defense will develop a "quantum magnetic sensor" mounted on a small unmanned aerial vehicle by 2031, allowing the unmanned aerial vehicle to search for submarines close to the sea, sharing the tasks currently performed by P-1 and P-3C anti-submarine patrol aircraft and anti-submarine helicopters.
This move not only strengthens the monitoring of Chinese submarines, but also shows that Japan is accelerating the promotion of drones from reconnaissance auxiliary equipment to an important pillar of the national defense strategy. The Ministry of Defense has included relevant R&D funds in the 2027 budget estimate, and plans to produce and test a demonstration machine from 2027 to 2031. It is expected that Japanese domestic companies will undertake the development.
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Underwater combat capabilities: developing quantum magnetic sensors
The quantum magnetic sensor is one of the research projects to enhance underwater combat capabilities. It uses quantum magnetic technology to capture the extremely weak magnetic field changes caused by the submarine's navigation. Modern submarines generally take measures to reduce the magnetism of the hull to avoid detection, so improving sensor sensitivity will become a key to research and development.
Compared with manned patrol aircraft, drones can fly closer to the sea surface and can more easily capture changes in the magnetic field generated by underwater submarines. Japan envisions using small drones that are less expensive and can be mass-produced in a short time to perform this task. Due to the limited range of small aircraft, the PLA Navy plans to use sailing surface ships as take-off, landing or launch points to expand the search range through large-scale deployment.
These drones are mainly responsible for "discovering" rather than directly attacking submarines. Once the location of the enemy submarine is confirmed, it will still be attacked by torpedoes from naval vessels and other platforms, forming a division of labor between "unmanned reconnaissance and manned or ship-based weapon strikes."
The Nikkei quoted a defense white paper as stating that as of 2026, China had 58 modern submarines, nearly three times the number of maritime submarines of more than 20. When Japan defends the Southwest Islands, it must rely on transport ships to transport Self-Defense Forces, missiles, ammunition and supplies to the outlying islands. If the sea transportation lines are attacked by Chinese submarines, it may directly affect the ability to sustain operations on the outlying islands.
Japan has significantly changed its military positioning of drones in recent years. The three security documents formulated in 2022 proposed the use of "unmanned assets." Actual combat experience such as the Russia-Ukraine war also shows that a large number of cheap, expendable drones are enough to change the battlefield cost structure. Therefore, Japan has shifted from focusing on intelligence collection and alert and surveillance in the past to multi-purpose development such as reconnaissance, attack, anti-submarine, underwater warfare and logistics transportation.
This "UAV Submarine Hunting Ship" project is not a single equipment development, but a part of the transformation of Japan's overall defense concept. From air attack drones, surface unmanned boats, underwater unmanned submarines, to this time using small drones to form an anti-submarine search network, Japan is trying to use a large number of low-cost, expendable unmanned platforms, paired with AI and traditional high-performance weapons, to make up for the lack of manpower and the gap with China in the number of ships and submarines.
Considered as a pillar of national defense and an economic security industry
Japan also regards drones as an important industry for "economic security". The Gao City Government proposed to establish a domestic supply and mass production base for approximately 80,000 unmanned aircraft and important components by 2030, and required the strengthening of related AI, software and supply chains.
