About Yahya ibn Da'ud, Almozarife of Monzon
In October 1149, the Count of Barcelona, assisted by other knights, conquered Lerida. . . Jews were employed in its fiscal administration. In the years immediately following the conquest of Lerida, we find the commander of the Order [Knights Templar] permanently leasing to Jews some of the lands recently appropriated from Arabs.
A Jew, by the name of Yahya ben David of Monzon, helped organize the administration of the district. He is the first Jew to be designated in official documents as "bailiff'. Yahya served primarily Alfonso II (1162-1196) of Aragon. His signature, in Latin characters, appears on documents dealing with taxes and other fiscal matters, on writs of exemption from taxes, on the charters of newly established Christian villages; and we find him, too, approving leases and transfers of land. He signed an official document fixing the boundaries of the city of Lerida under Moslem rule. In all, he appears to have fulfilled an important function in the apportionment of the conquered territory. He was himself the beneficiary of extensive grants of land in the vicinity of Lerida, with permission to rent them to whomever he desired, Christian, Jew, or Saracen. He also owned wine cellars in the Jewish citadel of Lerida.
Abraham bar Hiyya Ha-Nasi Albargeloni, a cousin of Yahya ben David, had already worked out the mathematics of land surveying and this knowledge, passed onto Yahya ben David, was critical in the latter's acquisition of lands. Accurate land surveys lead to fewer disputes over taxes.
The way in which Templar convents were founded in order to administer, and sometimes to defend, the possessions of the Temple in a particular district meant that with a few exceptions -- such as the subjection of Torres de Segre to the convent at Miravet -- the estates belonging to a convent were concentrated in one area, and the possessions of different houses did not overlap geographically. It did not mean, however, that any attempt was made to ensure that all convents had possessions of approximately the same value. It is clear from Hospitaller valuations which survive from the early fourteenth century, and from references to the leasing of Templar estates by the Crown after the arrest of the Templars, that the incomes of different convents varied considerably.
While the revenues of Monzón were assessed by the Hospitallers at 2,500l. and those of Miravet at 2,000l., Boquiñeni, on the other hand, was valued at only 50l. and Añesa at even less. At times the income of the smaller convents was scarcely sufficient to maintain a community. In 1277 it was said that the convent of Boquiñeni had fallen into 'the greatest poverty', and it was necessary to use revenues drawn from other convents to pay off Boquiñeni's debts and to undertake essential expenditure there. Although some convents with small incomes were situated in the more southerly regions of the Corona de Aragón -- Alfambra was valued at 100l. by the Hospitallers and Villel at 150l. -- most of the poorer convents lay in the more northerly parts of Aragon and Catalonia. The convents of Selma, Castellón de Ampurias, Aiguaviva, and Novillas, as well as Boquiñeni and Añesa, were among the least wealthy Templar communities.
The reason for the creation of a number of small convents in these areas is perhaps to be found in the fact that in the north Templar possessions were more scattered than in the more southerly districts, where they tended to be concentrated in lordships granted by the Crown. It was probably more convenient to establish a number of convents than to try to administer these scattered possessions from just a few houses, which would have had lands at a considerable distance. There were therefore by the later part of the thirteenth century few places in the Corona de Aragón that were very remote from a Templar convent. It was only in parts of the extreme north and in the extreme south, in the southerly region of Valencia, that there was an absence of Templar foundations.
Knowledge of the inner-workings of the Templar Organization empowered Don Yahya "El Negro" with the information critical to launching "The Knights of Santiago de Campostella" under King Afonso Henriques in order to counter the financial, and physical, power of the Templars.
Templars settled in Castile by 1129, in Rochelle by 1131, in Languedoc by 1136, at Rome by 1138, in Brittany by 1141, and in Germany at perhaps a still earlier date.
Alphonso I, of Aragon and Navarre, if we may trust the Spanish historians, bequeathed them the third of his kingdom spread (Mariana, x. c . 9) . Raymond Berengeur IV., count of of Barcelona, and Alphonso's successor in Aragon, whose father had been admitted to the order of Knights Templar, granted them the castle of Monzon (1143), and established a new chivalry in imitation of theirs Monzón castle where Jaime I (James I) lived as a Templar. Since 1143 it has belonged to the 'Orden del Temple'....and they hired jews to administer the lands for maximum tax-yield.