The Theory and Practice of Just War in the Late-Medieval Crown of Aragon

In the post-modern world that we inhabit, war, it seems, still lives in the Middle Ages. Leaders of the free world have proclaimed—almost preached—a crusade against international terrorism and, in response, radical Islamist leaders have thrown down the gauntlet against Christian interlopers seeking to extend political control and godless culture over the traditional heartlands of the Prophet.¹ What these implacable enemies hold in common is the unshakable belief that their own cause is thoroughly just and that of their adversary systemically evil.

Despite its unpleasant rebirth in modern times, the idea of just war has a very long provenance, stretching back to such Renaissance scholars as Erasmus and Vives,² to such medieval thinkers as Thomas Aquinas,³ and finally to the virtual originator of just war theory, the late antique polymath, St. Augustine.⁴ From the High Middle Ages onward, this intrusion of philosophy and ethics into military matters gave rise to generally accepted standards by which war was waged and peace negotiated.⁵ With this growing regulation of the violent aspects of warfare, formerly unconsidered questions, such as the involvement of clerics in war, became the meat of both canon and Roman law.⁶

Far from exploring abstract philosophical concepts of just war in the medieval centuries, this paper will focus on the everyday realities of a multi-national conflict which affected much of the Iberian Peninsula in the mid-fourteenth century and came to be known by later historians as the War of the Two Pedros (1356–1365).⁷ This struggle, which pitted the Peninsula's largest realms, the related but vastly different states of Castile⁸ and the Crown of Aragon,⁹ provides a perfect lens to view the practice and perception of late-medieval warfare as it affected the rapidly evolving states of eastern Spain.

I

The great conflict that unsettled central and eastern Spain during the middle decades of the fourteenth century clearly reflected the weaknesses and aspirations of the war's two protagonists. While this long episode of war had clear economic and geopolitical antecedents,¹⁰ it soon became a struggle of wills between men whose backgrounds were uncannily similar. Descending from a line of strong-armed conquerors who had made their reputations by engaging in a sometimes intense and always profitable war on Spanish Islam,¹¹ both Pere III "the Ceremonious" (1336–1387) and Pedro I "the Cruel" (1350–1369) were the products of loveless marriages and sterile family lives.¹² Though far better educated than the Castilian ruler, the Aragonese sovereign, like his "principal adversary," yearned to equal the record of martial glory won by his predecessors. The result of this emotional malnourishment coupled with a never-satiated desire for military success made Pere and Pedro into amateur family men, while transforming them into sovereigns who seldom shied away from war in defense of personal or national honor. Though the royal courts of these two rivals subsisted under a "tragic atmosphere," Pedro's vindictive cruelty, though occasionally mirrored in Pere's life, was markedly worse, bordering, as it did, on psychosis.¹³ Although Pere could unleash short bouts of brutality against those whom he judged to be traitors, he seldom used cruelty to assuage a drive for vengeance, but rather as a way of gaining political profit.¹⁴

Perhaps the greatest difference between the two men was their view of war itself in the cosmological scheme of things. Pedro seldom mentions the Almighty in regard to the struggle he so remorselessly waged against the exposed flanks of the Crown of Aragon. Pere, on the other hand, based his long and often unsuccessful defense on a theory of human conflict, which, though drawn from the centers of belief and education of the time, had been molded into a political and martial tradition by his relatives who...