North Korea test-fired what appeared to be a submarine-launched ballistic missile (SLBM). It would be the latest step in nuclear-armed North Korea's efforts to field SLBMs, which are seen as a potent nuclear deterrent because they can be difficult to detect or destroy.
Analysts and officials in South Korea believe the country is building an operational ballistic missile submarine. Here are the SLBMs that North Korea has displayed or tested, usually from submersible barges rather than from a submarine.