Abdi Aynte, recently with the Voice of America Somali service and soon to join Al Jazeera in Doha, authored a solid analysis of the Somali jihadist organization, al-Shabaab that calls for an Islamic caliphate and now controls about half of Somalia. He published an earlier version of the paper in the March 2010 issue of the Horn of Africa Journal. You can access it here.
Aynte concluded that al-Shabaab evolved from a little known extremist group to a global jihadist offshoot with links to al Qaeda. It cleverly exploited the irredentist Islamist movement of Somalia to provoke Ethiopia to attack so that it could activate its ultimate jihadist agenda, marginalize its moderate allies in the Union of Islamic Courts and expand the territory under its control.
While al-Shabaab successfully brought all Somali clans into its leadership, it isolated itself from most Somalis by becoming closely tied to al-Qaeda and adopting an extremist agenda.