This paper discusses capacity building for national security in Nigeria. The effort put into capacity building of a military is not too far from that put into nation building. This is because every segment of a nation's structure is replicated in the military. The military being an extension of a nation's source of power and foreign policy projection as well as a tool for providing a secure environment for economy to thrive, makes it mandatory for it' to be adequately equipped. Capacity building is that effort put up by the authority concerned to improve the operational readiness and hence efficiency of an organization and more appropriately in the case of the military, to improve its fighting capability. This therefore involves force structure, force level developments and equipping. It is virtually inaccurate and inappropriate to build a force structure or force level without a defense strategy to provide a guide or boundary conditions since strategy dictates the level and structure by which a military force can best be articulated.