Ethiopia–Sudan relations date back to antiquity. One of Ethiopia's principal trade routes ran west to Sudan and then to Egypt and the Mediterranean. Muslim merchants from Sudan have been an important part of Ethiopia's trade for many centuries.
History
Relations between Ethiopia and Sudan have not always been cordial. Military conflict broke out between Ethiopians and Sudanese in the 1850s. Sudanese Mahdists, or dervishes as they also were called, then advanced into Ethiopia in 1885, resulting in a series of battles between Sudanese Muslims and Ethiopian Christians over the next four years.
Relations improved during the twentieth century. Emperor Haile Selassie, who had been in exile during the 1936–41 Italian occupation of Ethiopia, returned with the help of Ethiopian, British, and Sudanese forces from Sudan. Relations became tense again in the late 1950s as Ethiopia supported the South Sudanese Anya Nya rebels in their battle against Khartoum. Selassie, however, helped broker the 1972 Addis Ababa Agreement that ended the first civil war between North and South.
Ethiopia's military government under Mengistu Haile Mariam (1974–91) strongly supported the SPLM/A against the government in Khartoum. The successor Tigray-dominated government, when it operated as a rebel movement, often took refuge in Sudan during its struggle to overthrow Mengistu. After taking power in 1991, it established cordial relations with Khartoum. This era of cooperation faded quickly as Islamic militants in Sudan tried to export their ideas to neighboring countries, including Ethiopia. Sudan's relations with Ethiopia reached a low in 1995 following Sudanese complicity in the attempted assassination of Egyptian president Hosni Mubarak as he was visiting Addis Ababa. The assassination incident and its aftermath was used by both Egypt and Ethiopia to seize lands in Sudan in 1995 (Halaib triangle on the border with Egypt and al-Fashaga on the border with Ethiopia respectively).
Concurrently, at the urging of the United States, Ethiopia and Eritrea joined Uganda in the so-called Front Line States strategy, which was designed to put military pressure on Khartoum. In 1997 Ethiopian forces joined the SPLA in a cross-border attack that resulted in the capture of the border town of Kurmuk and a second small town in Sudan's Blue Nile State.
Ethiopia normalized relations with Sudan by the end of 1998.
As of 2011, good relations between Sudan and Ethiopia continued in spite of Sudan's improved ties with Eritrea. Sudanese President Omar al-Bashir visited Addis Ababa twice in 2001. During a visit to Khartoum in 2002, Ethiopia's prime minister, Meles Zenawi, hailed Ethiopian–Sudanese ties. The two countries agreed to cancel entry visas and fees on traded commodities, and they stepped up plans to increase trade. Ethiopia began early in 2003 to import oil from Sudan. By 2009 Sudan supplied 80 percent of Ethiopia's demand for oil. The two nations signed an agreement ending a dispute involving their 1,600-kilometer border, and landlocked Ethiopia made plans to make greater use of Port Sudan as a transshipment point. Ethiopia, Sudan, and Yemen formed a regional group early in 2003 that they said was designed to “combat terrorism” in the Horn of Africa. In May 2010, Meles attended the swearing-in ceremony in Khartoum for al-Bashir following his election.