China’s naval buildup now includes a new class of attack submarine that employs both conventional and nuclear propulsion, according to defense officials.

Satellite images from earlier this year show efforts to salvage the new attack submarine at a shipyard in Wuhan, China.

A new Chinese nuclear-powered assault submarine sank at a Wuhan shipyard, raising questions about China's military capabilities and governance. Satellite photographs corroborated the salvage efforts following the crash.