The Mandailing and Angkola people, occupying the southern Batak lands, came under the influence of the neighbouring Islamic Minangkabau people as a result of the Padri War (1821–1837). Some Mandailing had previously converted to Islam, but the Padri war was a watershed event, with the Padri Wahabbis suppressing traditional customs ("adat") and promoting 'pure' Islamic faith. Over time Mandailing Islam, has been brought closer to the predominant Southeastern Shafi`i school of Islam as a result of Mandailing discourse with other Islamic practitioners and the practice of hajj, although traditional elements remain, such as dividing inheritance among all children, a Mandailing rather than Islamic practice. Islam caused the decline in importance of marga, with many Mandailing abandoning their marga in favour of Muslim names, much less so among the Angkola to their North.