The Democratic People’s Republic of Korea (DPRK or North Korea) is in the midst of developing programs for both submarine-launched ballistic missiles (SLBMs) and ballistic missile submarines (SSBs), potentially expanding the credibility, flexibility, and survivability of its current land-based nuclear force. Expansion of the DPRK’s nuclear force from a land-based monad to a land-based and sea-based dyad could increase the danger to the U.S.