A bellicist theory of diffusion: State formation in Northern Europe

By Eric Grynaviski and Sverrir Steinsson

How did the state become the dominant polity in the international system? The predominant theory of state formation, advanced by Charles Tilly, holds that states formed because of warfare and competition. Conversely, a new strand of research (e.g. Anna Grzymala-Busse, David Kang and Chin-Hao Huang) has argued that state formation happens when elites from one polity learn or emulate the organizational templates from another polity, thus diffusing state-like institutions across polities, even in the absence of war and competition.

In new research published in International Organization, we propose that the two strands of theory can be linked to more accurately explain state formation. War, we argue, is an important source of social diffusion. War encourages migration, shatters existing social structures, restructures trade networks, and provides opportunities for political and military leaders to learn about distant political units’ bureaucratic and organizational structures. We refer to this as a bellicist theory of diffusion.

We assess our bellicist theory of diffusion by examining the varied trajectories of several medieval polities: Denmark, Iceland, Norway and Sweden. What makes these cases useful for research purposes is that they have much in common, but differ on the timing in which institutions associated with the state (e.g. minting, standing armies, fortifications, national law codes) were adopted.

Origins of the state

Bellicist theories of state formation emphasize how selection and competition made the modern state the dominant organizational form in the international system.  The primary causal driver of state formation is warfare. Exposure to external threats led rulers to extract the means of war from their populations, thus facilitating institutional innovations in taxation, administration, and military organization. Political units with an advantage in extracting the means of war outcompeted other states. Less advanced states either get conquered by the advanced states or emulate their institutions in order to survive.

State formation in Northern Europe

We find that Viking era raids, settlements and conquests by Norwegian and Danish rulers in England, Europe’s most advanced kingdom, set in motion state formation processes in Norway and Denmark. The Vikings who raided England at the end of the eighth century were not the same Vikings who ruled England and Normandy by the eleventh. Victory changed them.

We show this by focusing on three sets of reforms: military reforms, economic reforms, and legal reforms. We use new scholarship from the fields of history, archeology, and numismatics to determine the timing and sequencing of these reforms.

The central intuition on which the diffusion mechanism rests is that war disrupts societies and generates interactions across borders. War is an inherently disruptive activity. War brings societies into direct contact and disrupts traditional social, economic, and political structures. We focus on three pathways to diffusion (see the figure below): elite contact, migration, and the formation of new economic networks.

One way war generates diffusion is by leading political elites to come into contact with one another, encouraging learning. In the medieval period, war provided an opportunity for such learning. Political elites traveled with their armies, giving them opportunities to learn about the military, economic, and political systems in different areas. A second way war encouraged diffusion and innovation was by encouraging migration. When one political unit conquered another, it often exported the skills and knowledge back home by encouraging or coercing individuals to return to their home kingdom. This migration spreads technical knowledge useful to rulers. The third way war encourages diffusion is through the development of new economic networks. Wars historically lead to the construction of new trade routes and ports, providing new opportunities for learning between societies.

Military reform

Military innovations connected to state-building are those that reduce the costs associated with defending territory, such as fielding a standing army or navy, and providing for fortifications during peacetime to reduce internal and external threats.

Two key revolutions in military affairs occurred in the 10th and 11th centuries that contributed to state formation: the construction of a network of fortresses in Denmark and the formation of standing armies. Recent archeological evidence has uncovered complex ring fortresses in Denmark dated to the late 10th century, during the reign of Harald Bluetooth. Scandinavian historians have now begun to characterize these fortresses as significant elements in Scandinavian state formation. England, especially Wessex, was the most likely model. King Alfred had erected a system of fortresses (burhs), created standing armies at the burhs, and established a naval force. Evidence also indicates that the Danes and Norwegians implemented standing militaries or naval forces that bore similarities to what existed in England. Swedes were much later in developing similar institutions, whereas Icelanders did not adopt these institutions prior to its absorption into the Norwegian kingdom.

To get a visual sense of the nature of this archaeological evidence, see the image below, of the Trelleborg remains in modern Denmark:


Many modern archaeologists believe the model was the burh or English fort encountered by the Danish Vikings when raiding England. Below is a modern rendering of Wareham’s burh:

Visual evidence is of course insufficient to demonstrate that the Danish forts were modeled on English designs; however, the post-Viking activity timing as well as the placement and apparent defensive use of these forts all point to English influence. In short, some of the first building projects in Viking areas associated with state-building were likely stimulated by English influence.

Economic reform

Economic reforms are intended to increase the economic capacity of the central state, such as raising taxes, minting coins, or the intentional development of the region’s economic or trade capacity. The paper focuses on minting coins, which was an essential element of economic activity during the period (and an effective early tax).

Before Viking successes in England, minting was relatively rare outside of one or two trading towns. After Viking successes, large numbers of mints flourished during the reign of Harald Bluetooth, Cnut, and Cnut’s son. There is clear evidence of diffusion, where Vikings brought technology home. When Cnut conquered English, he issued coins in his own name there, such as the below silver coin.

Silver Coin. 1019-1035. British Museum.

The coins in Denmark followed the same patterns. Coins developed in the 11th-century usually used English motifs, and some were clearly based on earlier English designs. For example, the following coin, also representing Cnut, was printed by a moneyer with an Anglo-Saxon name just a few years later, using a similar design; but, it was printed in Lund. Cnut brought the moneyers home with him.

Penny, 1019-1035. British Museum

Unlike the Danish rulers, Norway’s ruler did not travel to England. Instead, Norway’s King Harald traveled extensively, spending eight years in the Byzantine Empire. He introduced coinage upon his return. Svein Harald Gullbekk credits the innovations to Harald’s return with “new ideas” from his travels abroad.

Sweden briefly minted coins at the end of the 10th century, discontinued the operation by the early 11th century, and then restarted in the 12th century. According to Birgit and Peter Sawyer, the coinage delay in Sweden “reflects the late unification of that kingdom and the weakness of its rulers.” There was no minting of coins in Iceland, as trade was conducted through barter.

Legal reform

Legal reforms either create a national unification of laws so as to enhance central power or deepen the connection of a central power to the administration of a region through regional laws.

Unlike growing royal control over the economy and military modernization, legal reform is difficult to study during this period. It was the Dark Ages, and unlike money and fortresses, legal reforms leave less of an impression in the form of identifiable structures that can be discovered by archaeologists. That said, there is significant evidence the Viking invasions brought back legal knowledge to Scandinavia that led to substantial political and legal reforms that enhanced state-building.

The Swedes were later in adopting unified national laws. There was a legalistic culture in Iceland whereby chieftains settled their disputes through arbitrations in the Althing, but these arbitrations do not indicate that the state was taking on the role of enforcer of laws.

In sum

 In short, our findings agree with bellicists that war changes states. But, the competition mechanism is almost certainly wrong. In Northern Europe, new states were not emulating the most militarily successful units in the system. The winners often emulated the losers. What we see in the Norwegian and Danish cases is that in the aftermath of successful war and conquest that they had raised standing armies and fortifications back home, were minting currencies to control the economy within their territory, and made the first steps toward national law codes and judicial institutions. Victory changed them.

This generates an alternative to the was as competition hypothesis. War changes states, but through social learning instead of competition. As the Icelandic expression says, “Wisdom is welcome, wherever it comes from.”


  • Sverrir Steinsson is a PhD student in the Department of Political Science at George Washington University. He has diverse research interests across international relations, comparative politics, and organizational theory. Sverrir has research projects on state formation; the rise and fall of empires; digital platforms; and the foreign policies of small states. His research has been published or is forthcoming in International Organization, American Political Science Review, Cooperation and Conflict, Foreign Policy Analysis, European Security, and Scandinavian Journal of History, as well as in edited collections for Oxford University Press and Routledge.

  • Eric Grynaviski is an Associate Professor of Political Science and International Affairs at George Washington University.

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