Abstract Scholars and practitioners are placing emphasis on moving beyond defining development in narrowly economic terms. Instead, development emphasizes human capabilities and broad participation in decision‐making. This critical understanding of development calls into question assertions that war and preparation of war contributed to development in Europe (ca. 1500–2000) or in East Asia (post‐World War II). Only with a transition to democracy and turn away from militarism did these regimes begin to pursue developmental policies. In the twenty‐first century, wars are concentrated in the nations of the global south. Wars have been characterized as “development in reverse” – they destroy the institutions needed for development and reverse fragile gains in food security, child and maternal health, and environmental sustainability. For practitioners and scholars of development, the lessons are clear. Development is only possible when peace is firmly established. Development cannot be understood or promoted without a full consideration of war and social conflict.