The origins of the medieval war horse are obscure, although it is believed they had some Barb and Arabian blood through the Spanish Jennet, a forerunner to the modern Friesian and Andalusian horse. It is also possible that other sources of oriental bloodstock came from what was called the "Nisaean breed" (possibly akin to the Turkoman horse) from Iran and Anatolia, another type of oriental horse brought back from the Crusades. "Spanish" horses, whatever their breeding, were the most expensive. In fact, in Germany the word "spanjol" became the term for quality war horses. However, German literary sources also refer to fine horses from Scandinavia. France also produced good war horses. Some scholars attribute this to the strong Feudal society there, but an equally probable explanation is the historic influence of the Roman horse breeding traditions preserved by the Merovingians, combined with the addition of valuable Spanish and oriental bloodstock captured in the wake of the victory of Charles Martel over the Islamic Umayyad invaders at the Battle of Tours in 732. Following this battle, the Carolingians began to increase their heavy cavalry, which resulted in the seizure of land (for fodder production), and a change in tribute payment from cattle to horses.