Emperor Menelik emerged from the Battle of Adwa as an undisputed victor, for the first time in modern Ethiopian history, and was recognized by the world powers of the time. These powers rushed to sign friendship treaties with him and open missions to represent them in his court. The victory of Adwa had significant repercussions on the overall history of Ethiopia, saving it from the era of colonialism – along with Liberia – and influencing its international relations and status as one of two African countries not colonized. Internally, this victory also marked the beginning of the formation of Ethiopia with its current borders and the fulfillment of the dream of unification that had dominated the reigns of his predecessors, especially Emperors Theodore and Yohannes. The victory of Adwa had an impact not only on the country's political and economic future but also on the psyche of the people.

Menelik greatly benefited from Yohannes' wars with the Egyptians and Italians in the north. He took advantage of Yohannes' preoccupation with fighting them and also obtained weapons from them, which enabled him to begin his vast expansions that increased the kingdom of Shewa tenfold when he ascended its throne in 1865.

Expansion followed two paths: peaceful subjugation or military victory. Its vanguard began in the regions surrounding the kingdom of Shewa. To its south, the Qorafi tribes were militarily subjugated in 1887. Then Menelik turned west, where he subjugated the provinces of Hadiya and the Oromo Gamo and Kaffa successively in the southwest after the Battle of Ambo in June 1882. He then turned towards the Arsi tribes southeast of Shewa and defeated them thanks to modern weapons, despite their fierce resistance which lasted four years. He moved east towards Harar, which the Egyptians evacuated in 1885 after nine years of continuous Islamic rule. In the most brutal military campaign, the powerful southern kingdoms of Wolayta were subjugated in 1894, and cruel massacres were committed, described by a French historian who witnessed them as: "I had the feeling that I was watching a kind of hellish hunt, where humans were hunted instead of animals."

The scene was repeated in the provinces of Kaffa and Boran up to the borders of Lake Rudolf, which were subjugated in 1897, and its ruler was captured. In the same year, Ras Makonnen led a campaign against the sheikhdoms of Beni Shangul, Assosa, and Khamusha, exploiting the beginning of the collapse of the Mahdist state in 1898.