Military recruitment will become more difficult in times of demographic aging. The question arises whether demographic change will constrain the capacity of aging states like Germany to conduct foreign policy and pursue their national security interests. Since contemporary military operations still display a strong human element, particular scrutiny is given to the empirical analysis of the determinants of military propensity and military service among youth. An additional human capital projection until 2030 illustrates how the decline in the youth population will interact with trends in educational attainment and adolescent health to further complicate military recruitment in the future. A concluding review of recruiting practices in other NATO countries provides insight in best-practice policy options to reduce the military's sensitivity to demographic change. Following this approach, the book gives prominence to a topic that has thus far been under-represented in the greater discussion of demographic change today, namely the demographic impact on international affairs and strategic calculations.