Japan Order 300 REMUS Underwater Surveillance Drones from HII

Japan is making a significant investment in undersea defense technology by ordering more than a dozen REMUS 300 small uncrewed underwater vehicles (SUUVs) from Huntington Ingalls Industries (HII), a U.S.-based shipbuilding and defense technology company. The order, placed by Tokyo-headquartered Hitachi, marks a key milestone in the growing defense technology partnership between the United States and Japan.

While the exact user hasn't been officially confirmed, the order is widely believed to be linked to Japan's ongoing efforts to modernize and strengthen its maritime capabilities—potentially for the Japan Maritime Self-Defense Force (JMSDF). The multi-year agreement adds to the deep-rooted defense cooperation between the two allies amid increasing maritime tensions in the Indo-Pacific region.

The REMUS 300 is one of the most advanced small uncrewed undersea vehicles available today. It is specifically designed for versatility, endurance, and precision in undersea missions. Weighing just under 45 kilograms (99 lbs) and measuring 2.03 meters in length (6.66 feet), the system is compact yet highly capable. It can operate autonomously at depths of up to 305 meters (1,001 feet) for as long as 30 hours, depending on the battery configuration.

Powering the REMUS 300 is a modular lithium-ion battery system, available in 1.5 kWh, 3.0 kWh, and the highest-performance 4.5 kWh variant. The top-end configuration gives the vehicle a range of up to 165 kilometers (102 miles) at a cruising speed of 5 knots (9 km/h or 6 mph), making it suitable for long-range missions in complex underwater environments.

What sets the REMUS 300 apart is its modular design, allowing rapid integration of mission-specific payloads, such as sonar, environmental sensors, and cameras. This flexibility enables the vehicle to undertake a wide variety of missions, including mine countermeasures, intelligence gathering, reconnaissance, underwater mapping, search and recovery, and rapid environmental assessments. It can even be used alongside manned platforms like submarines to extend operational range and reduce the risk of detection.

The system is already in service with the U.S. Navy under its Lionfish program, where its reliability and multi-mission capabilities have been proven. Japan’s decision to procure these units reflects both a strategic alignment with U.S. underwater technologies and a growing emphasis on autonomous systems to counter emerging maritime threats.

Duane Fotheringham, president of the Uncrewed Systems group at HII’s Mission Technologies division, expressed gratitude for the deal, calling it a "key sales milestone" for the commercial REMUS 300 program. He noted the strong trust placed in the product by international partners like Japan, especially for critical missions like mine hunting and underwater surveillance.

As Japan continues to face maritime security challenges in the East China Sea and broader Indo-Pacific, the integration of REMUS 300 SUUVs is expected to enhance its naval situational awareness and operational flexibility, making its underwater defense strategy both smarter and stealthier.