As fighting began to flare Sunday around Kismayo, in southern Somalia, the final redoubt for the country’s diminished Islamic movement, elders within the city demanded that the Islamists go. Muhammad Arab, a leader of the Ogaden subclan, said 36 elders of various clans and subclans met over the weekend with Islamist leaders and tried to persuade them that resistance against the huge Ethiopian-backed force heading toward them was futile. "We told them that they were going to lose," Mr. Arab said, "and that our city would get destroyed." Kismayo, a scenic harbor town along the Indian Ocean that was once...