The inhibitions, caused by a series of Chera-Chola wars in the 11th century, resulted in the decline of foreign trade in Kerala ports. In addition, Portuguese invasions in the 15th century caused two major religions, Buddhism and Jainism, to disappear from the land. It is known that the Menons in the Malabar region of Kerala were originally strong believers of Jainism. The social system became fractured with divisions on caste lines. Finally, the Kulasekhara dynasty was subjugated in 1102 by the combined attack of Later Pandyas and Later Cholas. However, in the 14th century, Ravi Varma Kulashekhara (1299–1314) of the southern Venad kingdom was able to establish a short-lived supremacy over southern India. After his death, in the absence of a strong central power, the state was divided into thirty small warring principalities; the most powerful of them were the kingdom of Zamorin of Kozhikode in the north, Venad in the south, Kochi in the middle, and Kannur in the far north. The port at Kozhikode held the superior economic and political position in Kerala, while Kollam (Quilon), Kochi, and Kannur (Cannanore) were commercially confined to secondary roles. The Zamorin allied with Arab and Chinese merchants and used most of the wealth from Kozhikode to develop his military power. Kozhikode became the most powerful kingdom in the Malayalam speaking region during the Middle Ages. In the 14th century, Kozhikode conquered larger parts of central Kerala, which were under the control of the king of Cochin. He was forced to shift his capital (c. CE 1405) further south. In the 15th century, the status of Cochin was reduced to a vassal state of Kozhikode.