In December 2025, North Korean leader Kim Jong-un toured a shipyard and inspected the completed hull of a supposed 8,700-ton nuclear-powered “strategic guided-missile submarine.” North Korea’s state-controlled media hailed this sub as a breakthrough in Pyongyang’s naval nuclear ambitions. Just weeks earlier, U.S. President Donald Trump announced that the United States would share closely held nuclear propulsion technology with Seoul, clearing the way for South Korea to build its own nuclear-powered attack submarines (SSNs). Trump’s announcement was a long-overdue recognition of a strategic reality: in an era of nuclear-armed adversaries on the Korean Peninsula and a rapidly modernizing Chinese navy, South Korea cannot deter aggression with diesel-electric submarines alone. For decades, Seoul has operated some of the world’s most sophisticated conventional submarines. South Korea’s KSS-III-class subs are quiet, heavily armed with vertical-launch cruise and ballistic missiles, and equipped with advanced air-independent propulsion. They represent a remarkable indigenous achie
