This paper attempts to examine the effect of the rearing cost, defense expenditure and the foreign military threat on the fertility rate and the growth rate of the economy. In conformity with the viewpoint of Sandler and Hartley (1995), we observe the role of national defense on growth from the perspective of both the demand and the supply side. Within such a framework, we find that the rearing cost has a negative impact on the fertility rate, but it can enhance the growth rate. We also find an ambiguous relationship between military expenditure and economic growth, but military expenditure can increase the growth rate with defense sector production externalities are absent. Moreover, it is shown that the intertemporal elasticity plays an important role in determining the effect of a foreign military threat on economic growth.