Complex sentence: The Riau archipelago was historically a part of the Malaccan Empire since the expansion during the time of Tun Perak in the 15th century, following the demise of the Malaccan Sultanate by the Portuguese conquistadors in 1511, the Malay polity centre was shifted to Johor Sultanate.
Split into simpler sentences: The Riau archipelago was historically a part of the Malaccan Empire since the expansion during the time of Tun Perak in the 15th century. Following the demise of the Malaccan Sultanate by the Portuguese conquistadors in 1511, the Malay polity centre was shifted to Johor Sultanate.