Somalia has a long history of internal instability; in some instances, clan feuds have lasted more than a century. Most of this turmoil has been associated with disagreements and factionalism between and among the major branches of the Somali lineage system, which includes pastoral nomads such as the Dir, Daarood, Isaaq, and Hawiye, and agriculturalists such as the Digil and Rahanwayn (see The Segmentary Social Order , ch. 2). In more recent times, these historical animosities have expressed themselves through the emergence of clan-based dissident and insurgent movements. Most of these groups grew to oppose Siad Barre's regime because the president refused to make political reforms, unleashed a reign of terror against the country's citizenry, and concentrated power in the hands of his Mareehaan subclan (the Mareehaan belonged to the Daarood clan). After Siad Barre fled Mogadishu in January 1991, the Somali nation state collapsed, largely along warring clan lines.