After the fall of Malacca in 1511, the Riau islands became the centre of political power of the mighty Sultanate of Johor or Johor-Riau, based on Bintan Island, and were for long considered the centre of Malay culture. Like Malacca before it, Riau was also the centre of Islamic studies and teaching. Many orthodox scholars from the Muslim heartlands like the Indian Subcontinent and Arabia were housed in special religious hostels, while devotees of Sufism could seek initiation into one of the many Tariqah (Sufi Brotherhood) which flourished in Riau. In many ways, Riau managed to recapture some of the old Malacca glory. Both became prosperous due to trade but there was a major difference; Malacca was also great due to its territorial conquest.On the northern part of Sumatra around the same period, the Aceh Sultanate was beginning to gain substantial influence over the Straits of Malacca. With the fall of Malacca to Christian hands, Muslim traders often skipped Malacca in favour of Aceh or also of Johor's capital Johor Lama (Kota Batu). Therefore, Malacca and Aceh became direct competitors. With the Portuguese and Johor frequently locking horns, Aceh launched multiple raids against both sides to tighten its grip over the straits. The rise and expansion of Aceh encouraged the Portuguese and Johor to sign a truce and divert their attention to Aceh. The truce, however, was short-lived and with Aceh severely weakened, Johor and the Portuguese had each other in their sights again. During the rule of Sultan Iskandar Muda, Aceh attacked Johor in 1613 and again in 1615.