This document examines how trade-offs always arise for states deciding whether to spend billions of dollars on a new weapon system, and the nuclear-armed sea-launched cruise missile (SLCM-N) is no exception. In the United States, proponents of this weapon have not made detailed arguments in its favor, but their main assertions are that the country needs some unspecified number of SLCM-Ns to deter Russia from invading a NATO country and China from attacking Taiwan—a so-called deterrence gap.