One of the major causes of the sudden economic growth was the slave trade. Following the rise of the Arab empires, the Arab elites created a major demand for slaves with European slaves particularly prized. As a result of Charlemagne's wars of conquest in Eastern Europe, a steady supply of captured Slavs, Avars, Saxons and Danes reached mostly Jewish merchants in Western Europe, who then exported the slaves via Ampurias, Girona and the Pyrenees passes to Muslim Spain and other parts of the Arab world. The market for slaves was so lucrative that it almost immediately transformed the long-distance trade of the European economies. The slave trade enabled the West to re-engage with the Muslim and Eastern Roman empires so that other industries, such as textiles, were able to grow in Europe as well.