THE military Orders of Calatrava and Santiago contributed substantially and effectively to the Castilian reconquest. Entrusted with responsibility for the defense of the most critical frontiers, they served in the vanguard of the armies of Alfonso VIII (1158-1214) and Fernando III (1217-52) which initiated and nearly completed the conquest of Andalusia.' As they grew in wealth and public esteem a natural rivalry developed between them and, while they often collaborated to achieve their common aims, from time to time jealousies and conflicts of interest arose to disturb their good relations. With the hope of encouraging their knights to live and work in greater harmony, the masters of Calatrava and Santiago on several occasions concluded hermandades or pacts of friendship and brotherhood. These documents shed light upon the causes of controversy between the Orders and describe the procedures devised to resolve difficulties. But even more importantly they reveal a continuing desire to achieve a true spiritual fraternity which could be translated into cooperative action on the field of battle. Thus a perusal of the documents conveys a richer understanding of the progress of the reconquest in the late twelfth and early thirteenth centuries. The earliest of the hermandadles was signed by Pedro Fernandez, the founder and first master of Santiago, and Nufno, comendlador of Calatrava, acting in the name of his master, Martin Perez de Siones.2 Dated 8 August 1182, the document records Alfonso VIII's seizure of Sietefilla near Cordoba in June of that year; probably knights of both Orders had taken part in the campaign and cooperation in arms may have encouraged them to settle outstanding differences. At issue were property rights in Ucles and Ocafia and perhaps too the independence of the Order of Santiago. In January 1174 Alfonso VIII had given the fortress of Ucles, located in the Tagus valley east of Toledo, to Santiago and it soon became the headquarters of the knights. On 30 April, three months after this donation, the king gave a tenth of the royal revenues in Ucles to Calatrava.3 A brief note contained in a collection of documents pertaining to Santiago makes it amply clear