Satellite imagery revealed that China’s newest nuclear-powered attack submarine, the first Zhou-class, sank while under construction, a U.S. defense official reported. This setback hampers Beijing’s efforts to expand its navy amid its assertive South China Sea claims. The U.S. strengthens regional ties and conducts freedom of navigation operations, angering China. The submarine likely sank between May and June, with cranes visible in satellite images. China’s rapid naval expansion is a key U.S. security concern. A Chinese Foreign Ministry spokesperson provided no information on the incident.