They didn't really do it to prevent the area from becoming a terrorist haven, though. In their effort to "prevent the country from becoming a terrorist haven", they provided support to the very warlords who killed those US Marines and dragged them around Mogadishu over a decade ago. And now that they've gotten rid of the more moderate Muslim alliance that was governing the area, they now have extremists who stone 13 year old girls for being raped governing some areas and working hard to take over the rest of the country.