The French generally adopted a form of indirect rule, allowing existing native structures to continue to exist within the colonial framework of governance providing that they acknowledged French supremacy. The Zarma of the Dosso Kingdom in particular proved amenable to French rule, using them as allies against the encroachments of Hausa and other nearby states; over time the Zarma thus became one of the more educated and westernised groups in Niger. However, perceived threats to French rule, such as the Kobkitanda rebellion in Dosso Region (1905–06), led by the blind cleric Alfa Saibou, and the Karma revolt in the Niger valley (December 1905–March 1906) led by Oumarou Karma were suppressed with force, as were the latter Hamallayya and Hauka religious movements. Though largely successful in subduing the sedentary populations of the south, the French faced considerably more difficulty with the Tuareg in the north (centered on the Sultanate of Aïr in Agadez), and France was unable to occupy Agadez until 1906. Tuareg resistance continued however, culminating in the Kaocen revolt of 1916–17, led by Ag Mohammed Wau Teguidda Kaocen, with backing from the Senussi in Fezzan; the revolt was violently suppressed and Kaocen fled to Fezzan, where he was later killed. A puppet sultan was set up by the French and the decline and marginalisation of the north of the colony continued, exacerbated by a series of droughts. Though it remained something of a backwater, some limited economic development took place in Niger during the colonial years, such as the introduction of groundnut cultivation. Various measures to improve food security following a series of devastating famines in 1913, 1920 and 1931 were also introduced.