This work presents a myth-busting account of how class conflict and economic development, and not only interstate rivalry, led to the emergence of the modern state system. Inspired by the groundbreaking historical work of Robert Brenner, Teschke argues that property relations provide the key to unlocking the changing meaning of 'international' across the medieval, early modern and modern periods. Challenging the reification of the Treaty of Westphalia, Teschke shows that international politics remained under the control of dynastic and absolutist political elites that were rooted in feudal property regimes.