Based on exhaustive examination of the archival records housed in Gondar, Ministry of Foreign Affairs, National Archives and Library Agency, IES, Däbrä Markos University and East Gojjam Zone Police Department and extensive field work interviews, this study critically examines the deep rooted boundary dispute and frontier claims between Ethiopia and the Sudan with a special focus on the stretch of the frontier zones from the River Sätit in the north to the Blue Nile (Abay), 1898-1991. The closing years of the nineteenth and the first decade of the twentieth centuries were an eventful period in the modern state formation history of Ethiopia. Through a series of tireless diplomatic negotiations that explained international boundaries with the European colonial powers who controlled its neighboring kingdoms/territories, Ethiopia achieved its existing political map in the post Adwa period. Despite the fact that Ethiopia is one of the ancient countries in the world, its exact territorial limits remained undefined in all directions until the post Adwa period. Among the international boundary making efforts, the boundary negotiation that Ethiopia signed with Britain on behalf of the Sudan in May 1902, caused unending controversy, conflicting interpretations and divergent views in the late 1950s. The boundary negotiation and the resultant demarcations made by an Irish geographer, Major Gwynn in 1903 and 1909 representing only one side and violating the May 1902 treaty posed a serious complications when the Ethiopian government initiated commercial agricultural development in Sätit-Humära, West Armacheho, Mätäma and Maţäbia frontier districts in the late 1950s. Sudan, which achieved its independence in January 1956 became very sensitive to the boundary issue and challenged the Ethiopian frontier farmers and the imperial regime to respect the Gwynn line. When Ethiopian farmers continued commercial agriculture in the frontier territories, the Sudanese government built garrison centers and settled semi-pastoralist communities in the disputed areas. In response, the Ethiopian government attempted to check the Sudanese threat by arming and equipping the local Nätch läbaš and the Cheqa Šum units. In May 1967, the Ethiopian government deployed units of the police force in some disputed zones such as Gälan Zäraf, Rädam, Abdärafi and Mätäma Yohannes. On both sides of the border, the frontier lands became not only a source of economy, but also a symbol of identity building and self-definition. The boundary issue becam