trade in a variety of goods. The empire supplied the port of Malacca with rice and other foodstuffs, along with luxury goods such as rubies, sapphires, musk, lac, benzoin, and gold to trade. In return, the lower part of the empire imported Chinese manufactures and Indonesian spices through its ports. Additionally, merchants from West Asia and India exchanged large quantities of Indian textiles for Burmese luxury products and eastern goods. The arrival of the Portuguese in the 16th century further strengthened the empire's position, both commercially and militarily. Spread of Islam By the 8th century CE, less than 200 years after the establishment of Islam in Arabia, the first Islamic traders and merchants who adhered to Mohammad's prophecies began to appear in maritime Southeast Asia. However, Islam did not play a notable role anywhere in mainland Southeast Asia until the 13th century. Instead, widespread and gradual replacement of Hinduism by Theravāda Buddhism reflected a shift to a more personal, introverted spirituality acquired through individual ritual activities and effort. In addressing the issue of how Islam was introduced into Southeast Asia, historians have elaborated various routes from Arabia to India and then from India to Southeast Asia. Of these, two seem to take prominence: either Arabian traders and scholars who did not live or settle in India spread Islam directly to maritime Southeast Asia, or Arab traders that had been settling in coastal India and Sri Lanka for generations did. Muslim traders from India (Gujarat) and converts of South Asian descent are variously considered to play a major role. A number of sources propose the South China Sea as another route of Islamic introduction to Southeast Asia. Arguments for this hypothesis include the following: Extensive trade between Arabia and China before the 10th century is well documented and has been corroborated by archaeological evidence (see, for example, Belitung shipwreck). During the Mongol conquest and the subsequent rule of the Yuan dynasty (1271–1368), hundreds of thousands of Muslims entered China. In Yunnan, Islam was propagated and commonly embraced. Kufic grave stones in Champa, modern-day Vietnam, are indices of an early and permanent Islamic community in mainland Southeast Asia. The founder of the Demak Sultanate in Java was of Sino-Javanese origin. Hui mariner Zheng He proposed ancient Chinese architecture as the stylistic basis for the oldest Javanese mosques during his 15th-century visit to Demak, Banten, and the Red Mosque of Panjunan in Cirebon,