This missile-armed underwater drone could be quieter and harder to track than a submarine

China has criticized two of Japan's defense initiatives this week: plans to arm submarine drones with long-range missiles, and an agreement to test hypersonic weapons on Australian soil. Analysts say the moves could threaten Chinese naval forces operating within the first island chain, a strategic corridor stretching from Japan through Taiwan, the Philippines, and Borneo.

China's Ministry of National Defense spokesman Zhang Xiaogang raised the criticism at a briefing, saying Japan had "openly expanded its military arsenal." He called the moves dangerous and said they bore a "striking resemblance" to Japan's pre-World War II militarization. Zhang did not explain why these programs would pose challenges for the People's Liberation Army.

No hypersonic weapon yet

Japan has rapidly expanded its long-range strike capabilities since adopting a "counterstrike capability" in its 2022 security strategy. That policy allows strikes on military targets in an adversary's territory for self-defense following an armed attack, while ruling out pre-emptive strikes.

Japan has already deployed the domestically developed Type-25 hypervelocity gliding projectile, which entered service in March. The country does not currently have any system it officially designates as hypersonic in active service, according to analysts. More advanced systems remain under development, including the Block 2 HVGP, expected to fly at hypersonic speed, and a separate scramjet-powered hypersonic cruise missile.

Two underwater ambitions

Kyodo News reported that Tokyo plans to develop an underwater-launched hypersonic missile. Analysts described it as a hypersonic cruise missile fired from a crewed submarine. Separately, Kyodo reported that Japan intends to research technology enabling unmanned underwater vehicles to launch long-range missiles of their own.

Yoshihiro Inaba, the Japan correspondent for Naval News, said the country's defense technology agency is already developing a modular UUV for surveillance, submarine tracking, and mine-laying. Plans to arm that vehicle remain at an early stage, he said.

If armed, Inaba said, UUVs could pose a "persistent threat" to Chinese naval vessels near Japan's Nansei Islands or supporting a move against Taiwan. Timothy Heath, head of defense research firm Perceptum, said such vehicles could be hard to detect, since they may be quieter than submarines and launched from unexpected locations. Their lower cost could let Japan field far more of them, and simultaneous launches could threaten to overwhelm a target's defenses.

Split views on threat

Christopher Hughes, a professor at the University of Warwick, said China was "clearly irked" by these capabilities and was "probably right to fear them." He said lessons from Ukraine are shaping what Tokyo calls its "new ways of warfare." Japanese planners, he added, are studying how Ukrainian drones constrained Russia's Black Sea Fleet.

Inaba said planned Block 2A and Block 2B HVGP variants could reach roughly 1,240 miles (2,000 km) and 1,860 miles (3,000 km), respectively. Masashi Murano, a senior fellow at the Hudson Institute, offered a more measured take. He argued Japan's future hypersonic weapons would hold their greatest value in anti-ship strikes, not land attacks. Targeting China's naval forces directly, he said, would be the more efficient path to inflicting real losses.

An Australia complication

China also criticized Japan's plan to test hypersonic weapons in Australia. Japanese Defense Minister Shinjiro Koizumi and his Australian counterpart, Richard Marles, agreed August 18 to let Tokyo use Australian missile ranges over the next decade. The arrangement covers Japan's hypersonic program specifically. Koizumi called the move "groundbreaking."

Inaba said testing in Australia would make Chinese intelligence collection considerably harder than monitoring similar activity near Japan. The arrangement, he added, also reflects a deepening Japan-Australia alignment likely to draw its own concern in Beijing.