We propose a macrodynamic model of Kant's theory of the relationship between war and democracy. War and democracy have always been linked in some ways, from Athen's democratic empire in the 5th Century BCE, through the industrialization of war in the 19th and 20th centuries to today's nuclear powers, all forms of political regimes have been involved in war. Various macroeconomic models have accounted for the costs and benefits of war, and we extend them by introducing regime-specific sensitivity to human loss, which affects the desirability of war. We show the model can account for multiples wars throughout history.