until modern times. Because Islam prohibited taking Muslims as slaves, slave hunters focused their capture on the Orang Asli explaining the Malay use sakai to mean "slaves" with its present derogatory connotation. In the early 16th century Aceh Sultanate, located in the north of the island of Sumatra, equipped special expeditions to capture slaves in the Malay Peninsula, and Malacca was at that time the largest center of the slave trade in the region. Raids on slaves in the villages of Orang Asli were common in the 18th and 19th centuries. During this time, Orang Asli groups suffered raids by the Malay and Batak forces who perceived them to be of lower in status. Orang Asli settlements were sacked, with adult males being systematically executed while women and children were taken captive and sold into slavery. Hamba abdi (meaning, bondslaves) formed the labour force both in the cities and in the households of chiefs and sultans. They could be servants and concubines of a rich master, and slaves also did labour work in commercial ports. However, the relationship between the Malays and Orang Asli was not always hostile, as many other groups enjoyed peaceful and cordial relation with their Malay neighbours. With the easement of mobility and contact between various groups of people, the walls that separated the myriad of historical Austroasiatic and Austronesian tribal communities who once dwelled across the peninsula were dismantled, being gradually drawn and integrated into the Malay society, identity, language, culture and belief system. These Malayised tribes and communities would later be part of the ancestors of present-day Malay people. The new situation prompted many Orang Asli to migrate further inland to avoid contact with outsiders. These other smaller, closely related tribes; often located further inland compared to their coastal Malayised cousins, managed to be spared from the Malayisation process due to their secluded geographical location and nomadic and semi-nomadic lifestyle, hence preserving and developing their own endemic language, customs and pagan rituals. As the Malays advanced into the country, the Orang Asli slowly retreated further and further, concentrating mainly in the foothills and mountains. They were fragmented into small isolated tribal groups that occupied certain ecological niches, such as the river valley and had limited contact with neighbouring outsiders. Malay settlements were usually located on the coast or along rivers, as the Malays rarely crossed into the interior jungles. Nevertheless, some Orang Asli groups