From Mercenary to Citizen Armies: Explaining Change in the Practice of War

Mercenary armies went out of style in the nineteenth century; it became common sense that armies should be staffed with citizens. I argue that even though realist explanations focusing on the fighting prowess of citizen armies and sociological explanations focusing on the fit between citizen armies and prevailing ideas can rationalize this change, they cannot explain it. I examine, instead, the politics behind the new reliance on citizen armies and argue that material and ideational turmoil provided important antecedent conditions for change. Beyond this, individual states were more likely to move toward citizen armies when they had been defeated militarily and when the ruling coalition was split or indifferent about the reforms tied to citizen armies. Finally, the apparent success of citizen armies in France and then Prussia made do mestic conditions for reform easier to obtain in other countries, reinforcing the likelihood that the solution would be replicated. I conclude that the interaction between domestic politics and path dependency provides a promising source of hypotheses for explaining the conditions under which new ways of war emerge and spread.