In one of the most significant attacks against US forces in Afghanistan recently, CNN has learned that the Taliban twice targeted one of the most heavily guarded bases in the country late last month and that US military personnel working for the CIA were at the installation when it came under fire.In one of the most significant attacks against US forces in Afghanistan recently, CNN has learned that the Taliban twice targeted one of the most heavily guarded bases in the country late last month and that US military personnel working for the CIA were at the installation when it came under fire.