His reign was dominated by the struggle with Ahmad ibn Ibrahim al-Ghazi during the Ethiopian–Adal war until Ahmad's defeat and death in the Battle of Wayna Daga on February 21, 1543. Gelawdewos devoted time and energy to rallying his people against Ahmad, a determination his chronicler credits prevented Ahmad's forcible conversions from being permanent. With Ahmad's death, Gelawdewos was not only able to eject the leaderless Muslim forces from the Ethiopian Highlands, but also from the lowlands to the east, which included the Sultanate of Dawaro and Bale. He also turned his attention to the numerous Ethiopians who had crossed over to the Imam's side, either to further themselves or out of self-preservation. While some presented themselves to Gelawdewos expecting to be pardoned only to be executed, to many others he granted his safe conduct, according to Miguel de Castanhoso, "for there were so many [who had joined Imam Ahmad] that had he ordered all to be killed, he would have remained alone."