The rise and fall of armies

Over a thousand years, military employment rises, peaks, and then falls. I argue that rising military shares were driven by structural change out of agriculture, and the recent declines are driven by substitution from soldiers toward military goods. I document evidence for this substitution effect and introduce a model of growth and warfare that reproduces the time series patterns of military expenditure and employment. The model also correctly predicts the cross-sectional patterns, and that military employment and expenditure shares are decreasing in income during wars. Finally, I show that faster economic growth can reduce military expenditure in the long run.