‘Bella gerant alii.’ In 1516, by means of traditional dynastic finagling, the house of Habsburg acquired the thrones of Castile and Aragon, or Spain for short: the most bellicose and spectacularly expanding state in Latin Christendom. Henceforth, it seemed, the Habsburgs would no longer be able to leave war to others.

Since concluding Castile’s civil conflicts in the 1470s, the Spanish monarchs had, by force of arms, reconquered parts of French Catalonia, and added other acquisitions to their realms: southern Navarre, the western Canary Islands, Melilla, much of the Caribbean, and the kingdoms of Granada and Naples. For what came to be known as the Spanish monarchy it was the start of the most sustained period of success – measured by the crude, but decisive, standards of victory in the field and expansion on the frontiers – any Western European state had achieved since the Roman Empire.

Around 1900, scholars commonly marked modern history from the French invasion of Italy in 1494. The size of the army that crossed the Alps – about 30,000 men – and its use of field artillery to batter down the curtain walls of ancient towns was, supposedly, unprecedented. As France’s claims in Italy were subsequently challenged by Spain and the Holy Roman Empire, the duchy of Milan and other Italian states collapsed, or changed hands, with astonishing abruptness. Today, it is no longer clear that the campaigns of the Wars of Italy (1494–1559) were so sharply differentiated from those of the last phase of the Hundred Years’ War (1415–53). But the political cataclysms of our own time seem to confirm Niccolò Machiavelli’s insights into the precariousness of power at the turn of the sixteenth century. No boundary was sacred, and no government lacked a portfolio of ideas for expansion, to be tested if circumstances seemed ripe. Since a power dominant in a given region often worked to keep things as they were, one might distinguish between ambitious governments eager for war and cautious governments concerned to preserve what they had. Any move by a hegemonic power was taken by its rivals as an attempt to reduce them to abject servitude.

A positive shock to a society’s supply of human capital can come from exogenous and unanticipated immigration. One such case arose from Louis XIV’s precipitous revocation of the Edict of Nantes, which forced French Calvinists – Huguenots – to convert or to flee. Many fled to the Protestant regions of Germany, where – owing to the Huguenots’ renowned expertise and entrepreneurship – they contributed greatly to subsequent economic development. Only some of Germany’s many Protestant cities, however, welcomed the refugees. Analysis of sixty cities’ attitudes contradicts the idea that powerful guilds opposed, or that pre-existing human capital favored, the admission of the Huguenots. Rather, a city was likelier to welcome them the closer it lay to a major trade route, or the more of its population it had lost in the Thirty Years’ War. Territorial rulers almost unanimously welcomed the Huguenots and often compelled reluctant cities to admit them. Animated by the ideas of Seckendorff, rulers saw in the Huguenots both a welcome influx of human capital and a way to undermine the craft guilds, which Seckendorff regarded as a major impediment to economic growth.