What does China’s submarine missile test mean for its nuclear triad expansion?

China recently conducted a rare launch of a ballistic missile from a nuclear-powered submarine into the deep Pacific. This action serves as a public demonstration of the operational readiness of China's sea-based nuclear deterrent, a crucial component of its second-strike capability. Analysts suggest this test signals China's ongoing efforts to establish a fully operational nuclear triad. The launch is also expected to reinforce calls in Washington and among US allies for increased defense investment and enhanced security coordination, particularly in light of rising regional tensions and concerns about Beijing's military expansion. The test specifically sent a strategic message to the United States and regional neighbors, including Japan.