As the importance of horse breeding to successful warfare was realized, planned breeding programs increased. Many changes were due to the influence of Islamic culture through both the Crusades and the Moorish invasions of Spain; the Arabs kept extensive pedigrees of their Barb and Arabian horses via an oral tradition. Some of the earliest written pedigrees in recorded European history were kept by Carthusian monks, who were among those who bred the Spanish Jennet. Because they could read and write, thus kept careful records, monastics were given the responsibility for horse breeding by certain members of the nobility, particularly in Spain. In England, a common source of warhorses were the wild moorland ponies, which were rounded up annually by horse-breeders, including the Cistercians, for use as campaign riding horses, or light cavalry; one such breed was the Fell pony, which had similar ancestry to the Friesian horse.