Given the frequency and virulence of the Ethiopian raids, it was natural that the first pan-Somali or Greater Somalia effort against colonial occupation, and for unification of all areas populated by Somalis into one country

Should have been directed at Ethiopians rather than at the Europeans; the effort was spearheaded by the Somali dervish resistance movement. The dervishes followed Mahammad Abdille Hasan of the puritanical Salihiyah tariqa (religious order or brotherhood). His ability as an orator and a poet (much-valued skills in Somali society) won him many disciples, especially among his own Dulbahante and Ogaden clans (both of the Daarood clan-family). The British dismissed Hasan as a religious fanatic, calling him the "Mad Mullah." They underestimated his following, however, because from 1899 to 1920, the dervishes conducted a war of resistance against the Ethiopians and British, a struggle that devastated the Somali Peninsula and resulted in the death of an estimated one-third of northern Somalia's population and the near destruction of its economy. One of the longest and bloodiest conflicts in the annals of sub-Saharan resistance to alien encroachment, the dervish uprising was not quelled until 1920 with the death of Hasan, who became a hero of Somali nationalism. Deploying a Royal Air Force squadron recently returned from action in combat in World War I, the British delivered the decisive blow with a devastating aerial bombardment of the dervish capital at Taleex in northern Somalia.