Russia may be providing China with submarine quieting technology, a development that could significantly erode a key advantage held by the U.S. Navy in undersea warfare, according to retired Rear Adm. Mark Montgomery. This technological transfer, if confirmed, could have critical implications amid rising tensions over Taiwan.
Montgomery, co-author of the book "Axis of Aggressors," expressed concern that Russia is supplying China with technologies that enhance its submarine stealth capabilities. "Any weakening of our asymmetric advantage in undersea warfare is a big deal," he told Fox News Digital, highlighting the U.S. Navy's reliance on technological superiority and stealth for its submarines. China has long sought to improve its submarine propulsion and quieting systems, and Russian assistance could help Beijing close this gap.
Adm. Samuel Paparo, commander of U.S. Indo-Pacific Command, has echoed these concerns, telling the Senate Armed Services Committee in April 2025 that China was receiving "potentially submarine quieting help" from Russia. Paparo noted that China's support for Russia's war effort, including providing machine tools and legacy chips, is part of a broader exchange where Moscow reciprocates with military technology in areas of Russian strength. He described the relationship as a "transactional symbiosis."
The Chinese Embassy stated that military cooperation between China and Russia adheres to principles of non-alliance, non-confrontation, and non-targeting of third parties, contributing to national sovereignty and regional stability. The embassy urged that China-Russia military cooperation be viewed objectively and rationally, and called for an end to baseless speculation. They reiterated that Taiwan is an internal Chinese affair and urged the U.S. to maintain stability in bilateral relations and across the Taiwan Strait.
China has been instrumental in bolstering Russia's defense industrial base during the ongoing conflict in Ukraine. Paparo testified that Beijing supplied approximately 70% of the machine tools and 90% of the legacy chips that enabled Russia to sustain its war machine. Montgomery added that China's support extends beyond these supplies, citing increased foreign direct investment and trade, as well as components for Russia's ballistic, cruise, and hypersonic missiles.
In return, Russia has begun sharing military technology it previously hesitated to transfer, including the alleged submarine-quieting assistance. In October 2024, the Treasury Department reported that a Russian defense firm coordinated the production of attack drones in China, utilizing Chinese-made engines and components before their transfer to Russia for use in Ukraine. A 2025 investigation by RUSI, based on leaked documents, found that Moscow agreed to equip and train a Chinese airborne battalion and transfer technology that could aid Beijing in developing similar capabilities.
The ongoing conflict in Ukraine, now in its fifth year, has deepened Russia's reliance on Chinese industrial and financial support. This dynamic provides Russia with battlefield experience and military technologies that could prove valuable to Beijing in a potential future conflict over Taiwan. For the United States, the implications are particularly significant, as American submarines are central to its strategic planning for the Indo-Pacific region. Quieter Chinese submarines could complicate U.S. efforts to track, deter, and counter the People's Liberation Army Navy in the waters surrounding Taiwan.