Though it was not acceptable by the Ethiopian Empire, the Ethio-Sudan colonial border is not clear since it mainly relies on natural landmarks such as mountains, trees, and rivers.

[3] On 15 April 1891, Ethiopian Emperor Menelik II sent a letter to European heads of state which defined the actual boundaries of his empire as well as what he considered his area of influence.

The letter stated that the northwestern border of Abyssinia extends from the city of Tomat, located at the confluence of the Setit and Atbara Rivers, to Karakouj on the Blue Nile, and includes the Al Qadarif district.

[7] Following this, the Imperial government of Ethiopia felt obligated to support the rebel movement in South Sudan known as Anya Nya.

However, "an exchange of notes between Ethiopia and Sudan failed to settle the question of the Baro salient or make arrangements to stop banditry and establish peaceful coexistence among the pastoral people".