When Christovão da Gama marched inland with his 400 matchlockmen, Yeshaq not only provided him provisions and places to camp in his realm, but also about 500 soldiers and information about the land.
The Bahr Negus also joined Emperor Gelawdewos in the decisive Battle of Wayna Daga, where Ahmad ibn Ibrahim al-Ghazi, the leader of the Adal Sultanate, was killed and his forces scattered.
In return for ceding the town of Debarwa, Özdemir Pasha extended military support to the exiled Bahr Negus, and Yeshaq led an army into Tigray and the other northern provinces.
[5] When Sarsa Dengel the Great was made emperor, Yeshaq at first pledged his loyalty, but within a few years he once more went into rebellion, and found another ally in the ruler of Harar, Sultan Muhammad ibn Nasir.
From then onwards the governor of the provinces beyond the Tekezé was not allowed the sandaq (Banner) and nagarit (War Drum), and no longer had a place in Council unless especially called on by the Emperor.