According to a hypothesis developed by Jean Sauvaget, the umayyad "quṣūr" played a role in the systematic agricultural colonisation of the uninhabited frontier areas, and, as such, continue the colonisation strategy of earlier Christian monks and the Ghassanids. The Umayyads, however, increasingly oriented their political strategy towards a model of Client politics, of mutual interdependence and support. After the Umayyad conquest, the "quṣūr" lost their original function and were either abandoned or continued to serve as local market places and meeting points until the 10th century. Another type of Islamic fortress is the Qalat.