His great territorial expansion came at the expense of the Taifa Muslim kingdoms. Alfonso VI continued their economic exploitation by means of the system of "parias", and succeeded in subduing most of the Taifa kingdoms as his tributaries, enforced by the threat of military intervention. In 1074, he probably recovered payment of the "parias" of Toledo, and the same year, helped by troops of that city, he cut down trees on the lands of the Taifa of Granada, which consequently also began to pay him taxes. In 1076, the Emir of Zaragoza, who wished to seize Valencia without being disturbed by Alfonso VI, agreed to resume payment of the "parias". In 1079, he conquered Coria.