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The case of the medieval castle and the opportunity cost of warfare

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  1. skybrian
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    This is a book excerpt from Castles, Battles, and Bombs: How Economics Explains Military History. [...] The economic model is that both armies and the workers needed to build a castle needed to be...

    This is a book excerpt from Castles, Battles, and Bombs: How Economics Explains Military History.

    Historians may cringe, but the popular “castle and knight” image of the High Middle Ages does contain important elements of truth. Certainly, warfare was constant. To denizens of the twenty-first century, the scale of war a thousand years ago appears small, but the share of resources that was consumed by war was enormous. This consumption included not only the expenses of waging war but, almost invariably, the deliberate destruction of economic assets that accompanied invasions, and sometimes retreats as well. Power lay with substantial property owners. In the absence of powerful centralized governments local rulers could and did make war for almost every reason imaginable. To be sure, tradition, chivalry, and (occasionally) law did place some limits on warfare, but it was almost impossible for any medieval ruler of substance to avoid fighting for his entire career.

    Few were disposed to try. [...]


    The importance of the castle in European history, and not just military history, is impossible to overstate. The castle functioned as noble or royal residence, seat of government, defensive fortification, base of offensive operations, place of refuge, and tool of oppression. We know of no global calculation of the cost of castle building to European society as a whole, or even if such is possible. What we can do is consider the expenses that rulers poured into their construction, funds that then were unavailable for raising armies.

    The economic model is that both armies and the workers needed to build a castle needed to be paid. (They aren't farming, so they need to buy food.) The main cost is labor, and a lot of it, relative to what a medieval economy can spare. Rulers needed to raise lots of money to wage war (and defend against it), which they did any way they could:

    In the tenth or eleventh century a landholder might generate enough income to build a simple motte and bailey castle—consisting of an earthen mound, a circular wall or walls, and, in the center, a fortified tower as a final place for retreat—but revenues from estates could not keep pace with the growing costs of war. As landholdings of monarchs became less important, rulers became quite creative. The English kings exploited archaic land taxes, managed vacant bishoprics, pocketed profits from minting, collected every conceivable feudal due, taxed the laity for the crusades, and laid the foundation for the shift to universal taxation. This pattern—modernization of taxation due to war—can be seen in France and Spain as well. In France, the ordinary revenues grew from 86,000 to 400,000 livres tournois between 1180 and 1290, supplemented by a variety of special levies to fund wars and crusades. The Spanish monarchy achieved similar results, further stretching its money through devaluation. Monarchies grew in power as well as wealth. Only in the Holy Roman Empire did the pattern not occur, because the imperial “government” lacked the means to compel payment.

    Monarchs were thus able to acquire the funds for castles and armies and make war the province of the mighty alone. Ordinary nobles could not keep up. But it took time. Medieval European monarchs had few legal powers to tax and their organizations and institutions were too weak or disorganized to keep the flow of money steady. Payments in lieu of service were common, but these were so hard to keep track of that they disappeared in the fourteenth century. The creativity of royal treasurers was boundless, however. They chartered towns for a fee, took over church properties, used requisitions, paid for supplies with means other than cash, inflated the currency, borrowed money, and imposed public loans. Yet it was never enough. Warfare consumed the treasures of state.

    The chapter proceeds as follows. First we examine the concept of opportunity cost with respect to castle-based warfare. Next we present an accounting for the sheer number of castles, especially in relation to English kings. Then we assess the cost of castle building and show why, despite the truly enormous cost, the advantages outweighed the cost. Armies were not irrelevant but their cost was high and the advantages slight. Finally we point to where economic principles other than the principle of opportunity cost may be seen in the history of castle building.

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