Complex sentence: The Bruneian empire only had authority along the coastal regions of Sarawak held by semi-independent Malay chiefs, the interior hinterland of Sarawak was mainly dominated by tribal wars fought by Iban, Kayan, and Kenyah people who were aggressive in their territorial expansions.
Split into simpler sentences: The Bruneian empire only had authority along the coastal regions of Sarawak held by semi-independent Malay chiefs. Meanwhile, the interior hinterland of Sarawak was mainly dominated by tribal wars fought by Iban, Kayan, and Kenyah people who were aggressive in their territorial expansions.