spread islamic in indonesia

There is evidence of Arab Muslim traders entering Indonesia as early as the 8th century.^[4] Indonesia's early people were animists, Hindus and Buddhists.^[5] However it was not until the end of the 13th century that the process of "Islamization" began to spread throughout the areas local communities and port towns.^[4]
The spread, although at first introduced through Arab Muslim traders, continued to saturate through the Indonesian people as local rulers and royalty began to adopt the religion, subsequently their subjects would mirror their conversion. The "Islamization" process continued as Muslim traders married the local women, with some of the wealthier traders marrying into the families of the ruling elite.^[6]
The spread of Islam was, therefore, driven by increasing trade links outside of the archipelago; in general, traders and the royalty of major kingdoms were the first to adopt the new religion. Dominant kingdoms included Mataram in Central Java, and the sultanates of Ternate and Tidore in the Maluku Islands to the east. By the end of the thirteenth century, Islam had been established in North Sumatra; by the fourteenth in northeast Malaya, Brunei, the southwestern Philippines and among some courtiers of East Java; and the fifteenth in Malacca and other areas of the Malay Peninsula. Through assimilation Islam had supplanted Hinduism and Buddhism as the dominant religion of Java and Sumatra by the end of the 16th century. At this time, only Bali retained a Hindu majority and the outer islands remained largely animist but would adopt Islam and Christianity in the 17th and 18th centuries.
During this process "cultural influences from the Hindu-Buddhist era were mostly tolerated or incorporated into Islamic rituals".^[4]
Despite being one of the most significant developments in Indonesian history, historical evidence is fragmentary and generally uninformative such that understandings of the coming of Islam to Indonesia are limited; there is considerable debate amongst scholars about what conclusions can be drawn about the conversion of Indonesian peoples.^[7] The primary evidence, at least of the earlier stages of the process, are gravestones and a few travellers' accounts, but these can only show that indigenous Muslims were in a certain place at a certain time. This evidence cannot explain more complicated matters such as how lifestyles were affected by the new religion or how deeply it affected societies. It cannot be assumed, for example, that because a ruler was known to be a Muslim, that that the process of Islamisation of that area was complete; rather the process was, and remains to this day, a continuous process in Indonesia. Although it is known that the spread of Islam began in the west of the archipelago, the fragmentary evidence does not suggest a rolling wave of conversion through adjacent areas; rather, it suggests the process was complex and slow.
In the late fifteenth century, the powerful Majapahit Empire in Java was at its decline. After it had been defeated in several battles, the last Hindu kingdom in Java fell under the rising power of the Islamized Sultanate of Demak in 1520. Islam in Java then began to spread formally, largely influenced by the Wali Songo (or the Nine Saints).^[note]