The Diplomat:

South Korea’s “Three Axis” deterrence system is in trouble. North Korea’s recent claim to have tested a new undersea nuclear delivery system is the latest in a long series of developments that throw the credibility of this concept into question. The growing diversity, sophistication, and survivability of the North’s nuclear arsenal undermines the elements of the Three Axis system that rely on deterrence by denial, including preemptive strike and missile defense capabilities. To respond to these developments, Seoul should focus its efforts on deterrence by punishment, bolstering its retaliatory capabilities in order to dissuade Pyongyang from aggression.

South Korea’s plan to deter a North Korean attack revolves around the “Three Axis” system. This system ties together three military concepts. The first concept, commonly known as the “Kill Chain,” seeks to use advanced detection, targeting, and long-range strike capabilities to enable South Korea to preemptively destroy an imminent North Korean missile launch. The second concept, labeled “Korean Air and Missile Defense” (KAMD), employs ballistic missile defense systems to allow South Korea to shoot down North Korean missiles in-flight. The final concept, “Korean Massive Punishment and Retaliation” (KMPR), emphasizes the use of special operations forces and a diverse array of strike capabilities to deliver a debilitating retaliatory blow in the aftermath of a North Korean attack. 

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