[1] Described as the last “great” Gondarine monarch, Iyasu temporarily halted the trend of decline through his brilliance as a military leader, reestablishing control over rebellious vassals and conquering areas to the south of his domain.

[2] Iyasu fell out with his father in 1681, and according to the chronicles, the prince and his followers crossed the Blue Nile and found refuge in pagan controlled areas.

[7] Yohannes I died on 19 July 1682 and Iyasu ascended the throne, with the serag masare[note 3] Malkea Krestos putting the crown on his head.

The Tsehafi Taezaz's Hawarya Krestos and Walda Haymanot sent sealed letters to various countries to announce the death of Yohannes I, and that the reign of his son Iyasu I has begun.

In November, Iyasu I summoned the chiefs of Tigray, and interrogated them on the taxes then exacted at the customs posts (also known as the Kella system)[note 4].

[12][13] Iyasu I strengthen his control over his southern domains through his alliance with two influential Amhara warlords, Demetros of Merhabete and Negasi of Menz.

Having accepted the suzerainty of their northern monarch, Demetros was granted the old imperial title of Sahafe Lam while Negasi was honoured in Gondar with pomp and circumstance receiving gifts from the Emperor.

[16][17] Several ethnic groups suffering from persecution and raids in Oromo occupied territories, from the Kordidas Amharas in 1681 to the Talatas in 1695, aligned themselves with Iyasu's government, in hope of securing succour from the monarch.

In 1689, Iyasu's Armenian trade agent, Khodja Murad told the Dutch in Batavia that the king of Hadiya had ‘‘submitted of his own free will to the rule of Abyssinia.’’ after suffering defeats and pressures by Oromos.

Iyasu then carried out his main assault on the Oromos living in Wollo, who were so terrified by the fate of the Wechales, and so afraid of passing through the latter's burning fields, that they were unable to offer any resistance.

Solomon Getahun observes that "unlike his immediate predecessors, Iyasu's tenure was noted for endeavors to establish diplomatic ties with Christian monarchies like Louis XIV of France and Ethiopian delegates had been sent to foreign countries.

One of the benefits of these efforts was that Emperor Iyasu received a bell from Johannes Camphuys, governor of the Dutch East Indies, which was then donated to Debre Berhan Selassie Church in Gondar.

Poncet published an account of his visit to Paris in 1704, which included his personal impression of Iyasu the Great: In 1705, while he was campaigning in Ennarea against the Oromo.

Iyasu learned that his favorite concubine, Kedeste Kristos was suffering from a terrible illness, he abandoned his campaign and returned to Gojjam where he found her already dead.

According to some accounts, this was not Iyasu's intent, and he marched from his hermitage in Lake Tana towards to Gondar to protest this; in any case, during this time he fell sick and was assassinated at Tekle Haymanot's orders by his maternal uncle's, Dermen and Pawlos.

[33] Iyasu's death caused much distress in the capital, especially amongst the priests of Debre Berhan Selassie, who openly displayed his gifts to them, and mourned their dead monarch for a month.

The power of the monarchy was weakened by frequent coups d'etat: no fewer than twenty-five emperors were deposed in the century and a half between Iyasu I and Tewodros II.