Complex sentence: Dembo's succession of Savimbi had been pre-ordained by Savimbi and the UNITA leadership when, in 1997, Dembo was named Savimbi's successor in the event of Savimbi's death.
Split into simpler sentences: Dembo's succession of Savimbi had been pre-ordained by Savimbi and the UNITA leadership. In 1997, Savimbi and the UNITA leadership named Dembo Savimbi's successor in the event of Savimbi's death.