The founding fathers of international relations theory loved war but overlooked sex

Hans Morgenthau, the great US theorist of international relations, wrote that the key to the discipline was simple: Just assume that "statesmen think and act in terms of interest defined as power." Doing so, he implied, would unlock timeless and universal laws.

When it came to power in pre-modern Europe, Morgenthau and other IR theorists zoomed in on war and conflict, and the mistrust that resulted. They saw in these patterns of recurrent war a grim warning for any sort of attempts to improve international politics today. But their attempt to find simple lessons of history is complicated by the fact that the actual levers of power amid Europe's dynasties were often very different: marriage, sex, and family.

International relations were a far more literal concept when states not only fought but also married and had children. When the state hung on the body of the ruler, rulers had no private lives. Marriages could be strategic weapons. Failure to produce an heir could result in disorder or war. A flaccid penis or a barren womb was a national concern, not an individual one. These issues, often dismissed by scholars of international relations theory, changed the fate of nations.  One famous international relations text defines its concerns in the title as "Man, the State, and War." But the overwhelming concerns were often more women, the dynasty, and marriage.

Europe's dynastic past shows that change in international systems involves more than shifts in an eternal contest for power—it also entails far-reaching transformation to social systems that can change the rules of that contest. The norms taken for granted by theorists today are transitory and relatively recent. And it shows how women—ignored by the discipline's founding fathers—were key to those international relations, albeit not always happily.

Today, you can easily find modern maps of Europe in 1000 A.D. They show large chunks of a continent ruled by unfamiliar-sounding countries, but overall the maps look pretty familiar. Those maps are deeply misleading about the past. They impose our understanding of what politics should be on a world that was fundamentally different than our own.

Contemporary states are defined by their borders—what scholars call "territoriality"—but these policies were linked by relationships among rulers and ruled with complex and overlapping jurisdictions. And in those vast regions nominally under the jurisdiction of one power or another, in reality there could be dozens or hundreds of functionally independent polities, ranging from sovereign towns to bishoprics to duchies and kingdoms.

The reductionist view of international relations tells how those hundreds of polities consolidated into the few dozen European countries of today. It's a story that privileges war and conquest. It's plausible, but it's just as misleading as those maps. Conquest mattered in the consolidation of Europe, to be sure, and the strains of war did much to build up governments that grew more competent at taxing and raising armies. But ambitious rulers preferred other strategies to the costly gamble of war or the slog of pacifying conquered provinces.

European "states" were really dynasties that entwined rulers' personal and political selves—and that opened up new avenues for expansion. There was little concept of the "national" interest to which monarchs should be even nominally subordinate—just the interest of the rulers, nobles, and other elites (like the church), and the rumblings from below that might topple them.

Strategies that later eras could not imagine as part of statecraft could prove pivotal. Prime among these was conception. A child could combine realms; the absence of one could destroy them. In an era when family was the basis of politics, the most common crises were not economic or military, but biological—the failure of a ruler to produce an heir, or the failure of an heir to survive to adulthood. And as Marxist historian Perry Anderson notes, marriage was the "supreme device of diplomacy," because it could obtain the same ends of dynastic expansion as war—and at much lower cost.

Europe's states, then, did not just consolidate through a process of survival of the fittest determined by the grim contest of war. Dynasties could acquire more control and territory by marriage, inheritance, purchase, or even invitation. Depending as those processes did on chance and opportunity, that pattern of consolidation did not produce successive revisions of ever-more-rational drafts of modern states. Rather, as international relations theorist Daniel Nexon writes, a patchwork of inheritances and additions created "dynastic agglomerations."

The Habsburg dominions in the mid-16th century provide the best illustration of the principle. Around 1550, Emperor Charles V controlled contemporary Spain, Sardinia, Sicily, Naples, Milan, the Netherlands, and much of Austria, Germany, and Romania—along with vast swaths of the former Aztec, Inca, and other lands in the Western Hemisphere.

Dynastic marriages advanced dynasties' interests in many ways. Most obvious, they gave legitimacy to any children who might result, enabling political power to be passed from one generation to another. The Habsburg empire reached its greatest extent in Europe from a patchwork of inheritances, not a militarily optimal strategy—and its extent may have even been disadvantageous for extending their interests. It took great effort to get soldiers from Italy to a rebellious Netherlands, for instance.

Marriages could also provide valuable intelligence assets, as historian Paula Sutter Fichtner writes: "when accurate information from abroad was at a premium, a child at a foreign court could keep one apprised of events there." Dynastic marriages, which women played a critical role in arranging, also served as vectors for cultural exchange, part of the process by which an elite emerged and created a sense of "Europe" from the political divisions of the post-Roman world. The arrival of a new queen could shake up art and manners by bringing new ideas, creating cultural fusion while distancing cosmopolitan life at court from the cultures they ruled.

Most important, marriages between dynasties kept the peace. International relations scholar Hiroaki Abe argues that dynastic marriages blunted competition between ruling houses, thanks to the power of kinship ties.

Dynastic deterrence worked, Abe contends, because "dynastic wives and families of origin play[ed] the role of hostages." Waging war against a monarch related to a ruler by marriage could damage a dynasty's reputation, reducing the chances of a future advantageous marriage—and why destroy what one might inherit?

The net result, Abe writes, is that the ability of dynasts to marry each other made particular European conflicts less severe than they would otherwise have been. Statistical tests by scholar Joseph Gardner confirm that European rulers who were from the same patrilineal dynasty were least likely to fight each other.

The object of dynastic marriage was not only expansion but reproduction—literally. As historian Robert Bartlett writes in Blood Royal: Dynastic Politics in Medieval Europe, "[i]t was not elections or referenda that shaped political life, but the births, marriages and deaths of the ruling family."

A political world organized around the interests of a family line was one in which the prospect of dynastic extinction was the worst-case scenario. Contemporaries feared that dynasties that failed to produce clearly acknowledged heirs could spark warfare among rivals within an heirless realm and ambitious external powers that sought to place their dynastic candidate on the throne. Modern scholarship confirms these fears.

Evolution divides species into two types: those that spawn many offspring and expect few to survive and those that devote great effort to raising a small number of offspring in a highly competitive environment. European royalty was decidedly the latter. Each oldest male child bore the burden of a dynasty. Enormous efforts, from the medical to the astrological, were put into conception, and into steering the heir in the right direction.

Failures of dynastic reproduction were crises of fundamental governing institutions, and they had incredibly long-lasting effects. Political scientists Avidit Acharya and Alexander Lee estimate that regions of Europe with more male heirs hundreds of years ago are substantially richer on a per capita basis than those with shortages. The luck of a ruling family in producing an heir in the era of Galileo might explain why a region is richer or poorer than its neighbor even today.

There were other ways that reproduction could fail. Research into the Spanish Habsburg dynasty, for instance, shows that inbreeding probably influenced its decline after nine of 11 consecutive marriages were consanguineous, with some members of the dynasty produced by matches as genetically close as brother and sister. Even a frail but intelligent heir, like the hemophiliac Tsarevich Alexei of Russia, prompted worries that could lead to bad decisions, like inviting the spiritual healer Rasputin to court.

This all made the female body essential to European politics. Real women were trapped in those calculations. Girls aged 12 or even younger could be betrothed to future husbands they had never met and sent to live with their future family hundreds or even thousands of miles away, their bodies turned into little more than political vessels.

The imperative to produce an heir suggests that European politics revolved around sex, specifically procreation. But biology alone didn't prevail. Behind all of these calculations lay strict social rules about gender, religion, and inheritance.

After all, given how costly a failure to find an heir was, why couldn't European rulers turn to other means than monogamous, largely unbreakable marriage to produce legitimate heirs? After all, male rulers in most of the rest of the world used practices like polygyny (multiple wives) or concubinage to avoid the political instability that perennially brought many European states to ruin. Harvard University political scientist Yuhua Wang, for example, finds that Chinese emperors of the past millennium, some of whom had hundreds or even thousands of concubines, had little trouble providing male heirs, reducing a major cause of political instability.

A view of politics that ignores social life cannot explain this inability to adapt, stemming as it did from faith. Christianity banned such practices and imposed greater limitations on divorce and incest than its European predecessors on top. Christianity also frowned on interfaith marriages, contributing to the endemic warfare between Muslim and Christian rulers in Europe. After the Reformation, it heightened the stakes of marriage and childrearing, as the accession of a ruler with a different faith threatened to upset the entire realm.

Gender roles also collided with ruler ship. International relations scholar Diana Saco notes that Queen Elizabeth I's long rule in 16th-century England forced (male) political theorists to re-examine what sovereignty itself was to justify being led by a woman—and, Saco observes, Elizabeth's own refusal to marry pitted her dynastic responsibilities against her own desire to wield power.

The reductive view of international relations as driven only by a lust for power cannot explain why these sorts of religious rules or gender norms would matter. They did, nevertheless. International politics cannot be reduced to simple explanations that disregard everything about what makes social life meaningful, because those conditions are exactly what enables any action to be taken in politics at all.

Eventually, the rise of nationalism, bureaucracy, and forms of ruler ship other than monarchies displaced concerns over dynastic marriages and children. Today, nobody expects that keeping Canada together depends on Prime Minister Justin Trudeau, the eldest son of a former prime minister, producing a third generation of his dynasty. No analysts worry that the European Union is endangered because neither French President Emmanuel Macron nor German Chancellor Angela Merkel has children to offer in marriage.

Nevertheless, marriage, sex, and gender shaped the history of the European political system, however missing they have been from some theorists' account of the past. Questions about whose interests matter in international politics cannot be taken for granted. The identity of the powerful and the way their interests translate into strategy can change profoundly over time. They may yet shift again, for reasons we can only glimpse at right now. But at least we can get the politics of the past right, and give the women whose labour produced it their due.

TBS Sketch.

Paul Musgrave is a Professor of the University of Massachusetts. 

Disclaimer: This article first appeared on Foeign Policy, and is published by special syndication arrangement.