Militarily, al Shabaab's defeat seems to have been partly a result of regional and international power politics -- of Kenyan and Ethiopian attempts to expand their spheres of influence, and of American efforts to curtail potentially threatening Islamist terror groups. And it was partly a result of a largely unprecedented effort in African multilateralism. As of November of 2011, over 500 soldiers, mostly from Uganda and Burundi, had died in a mission to prop up one of Africa's most vulnerable governments and to help reverse Somalia's 20-year trajectory of state failure and anarchy. But al Shabaab's decline is just as attributable to far more prosaic factors: by all accounts, daily life under the al Qeada affiliate was miserable.

Al Shabaab blocked outside aid groups during the devastating famine of 2011, a move that forced starving Somalis to flee Shabaab-controlled areas if they needed help -- and that "led to a withdrawal of public support," according to Ademo. They imposed what Hogendoorn described as "very draconian Salafi interpretations of what is and is not permitted under Sharia law," levied high taxes, and impressed local youth into militia service (a 2010 Human Rights Watch report provides a similarly grim assessment of al Shabaab's rule). Physical security, the bedrock of al Shabaab's support, began to deteriorate thanks to the group's "increased deployment of suicide attacks and IED attacks that were yielding high civilian casualties," says Thomas. At the same time that the African Union, Kenya, Ethiopia and the U.S. were threatening al Shabaab's military hold on Somalia, much of the country, and, more importantly, many of the clans and local leaders who had sided with al Shabaab, decided they had had enough.

Still, even as African Union forces prepare for their attack on Kismayo, al Shabaab is providing a vicious reminder of just how tenuous this victory could end up being. On Thursday, at least 14 people, including several journalists, were killed in twin suicide blasts in downtown Mogadishu, which is no longer under the group's control. Abdi Aynte, a reporter for Al Jazeera, tweeted that the attack might have specifically targeted known haunts of Mogadishu's journalists. As Aynte wrote, this appeared to be an attack on a "soft target" -- a means of amassing a body count and instilling fear; a bid at derailing Somalia's fragile transition.

At this point, al Shabaab might prefer this sort of a campaign anyway. The group has a recent history of tactical retreats, Thomas explained, and has been able to maintain a force of as many as 12,000 fighters partly because "they've avoided engagements with forces with better weapons than them." The fall of Kismayo might not signal al Shabaab's military defeat so much as its transition into a full-blown terrorist insurgency, dedicated to a bloody, long-term guerrilla war against Somalia's fledgling government.