The first Ugandan soldiers to fly into Somalia 5 1/2 years ago came under attack as soon as they arrived: Militants fired mortars at the new mission's welcome ceremony. Today, backed by a sweeping multinational effort that includes $338 million in U.S. equipment, wages and training, the force of Ugandans, Burundians, Kenyans and Somalis that was deployed to take on the country's Islamic radicals can claim a degree of success that had initially seemed highly unlikely.