The Oromo conflict was an armed conflict between the Oromo Liberation Front (OLF) and the Government of Ethiopia. The conflict began in 1973, when Oromo nationalists established the OLF and its armed wing, the Oromo Liberation Army (OLA).
The Oromo people are an ethnic group that mainly inhabit Ethiopia, with communities in neighbouring Kenya and Somalia as well. They are the largest ethnic group in Ethiopia and the wider Horn of Africa; according to a 2007 census, they make up about 34.5% of Ethiopia's population, and others estimate that they make up about 40% of the population.
In 1967, the imperial regime of Haile Selassie I outlawed the Mecha and Tulama Self-Help Association (MTSHA), an Oromo social movement, and conducted mass arrests and executions of its members. The group's leader, Colonel General Tadesse Birru, who was a prominent military officer, was among those arrested. The actions by the regime sparked outrage among the Oromo community, ultimately leading to the formation of the Ethiopian National Liberation Front in 1967 and the Oromo Liberation Front in 1973.
In 1973, the Ethiopian military ousted the imperial regime and seized control of the country. The new regime promptly arrested Oromo leaders; subsequently, the Oromo Liberation Front (OLF) was formed during a secret conference attended by Oromo leaders, including Hussein Sora and Elemo Qiltu. A group of armed Oromo fighters in the Chercher Mountains were adopted as the OLF's armed wing, the Oromo Liberation Army (OLA). In 1974, the OLA increased its activities in the Chercher Mountains, prompting the Ethiopian regime to send its military to the region to quell the insurrection.
In June 1974, General Tadesse Birru, an Oromo nationalist who had been arrested by the imperial regime in 1966 along with other high ranking military officers, escaped from house arrest and joined Oromo rebels led by Hailu Regassa in Shewa. Birru and Regassa were later captured and executed by the Derg regime.
In late August 1974, an OLA unit came down from their stronghold in the Chercher Mountains and made their way closer to Gelemso, hoping that nearby fully grown crops would be able to hide them from Ethiopian soldiers as they advanced towards other nearby towns. Three of the unit's new recruits were unaccustomed to climbing long distances, so they spent the night around the bottom of the mountains, while the rest of the soldiers camped at the top.
When an OLA soldier was sent to retrieve the three recruits, it was discovered that they had been killed by Ethiopian militiamen who had followed the unit to Tiro. A large group of Ethiopian policemen and militiamen surrounded the OLA position in the mountains, and the two opposing groups began to exchange gunfire. A group of Ethiopian soldiers led by General Getachew Shibeshi later arrived, and began to shell the stronghold with mortar rockets, killing most of the OLA's members, including Elemo Qiltu. The event became known as the Battle of Tiro. Contingents of the OLA continued to fight the regime after the battle and later gained a massive influx of recruits and volunteers after the Derg regime executed Tadesse Birru and Hailu Regassa.
In 1976, the OLF established a stronghold in the Chercher Mountains and began reorganizing itself. A congress was created by Oromo leaders, which revised the 1973 OLF Political Program and issued a new detailed program. The program called for the "total liberation of the Oromo nation from Ethiopian colonialism". The conference is now known as the Founding Congress, and marked the beginning of modern Oromo nationalism.
In the 1980s, the OLF estimated that they had over 10,000 soldiers. They were poorly equipped in comparison to other rebel groups in Ethiopia at the time, such as the Eritrean People's Liberation Front (EPLF) and the Tigrayan People's Liberation Front (TPLF). The OLF also opened an office in Sudan in the 1980s, after its office in Somalia was closed down.
During the 1980s, the government of Ethiopia was accused of using scorched earth tactics, such as burning down entire villages and massacring inhabitants. The OLF also lost several prominent members due to government ambushes and heavy fire; the secretary general of the OLF at the time, Galassa Dilbo, was nearly killed in one such ambush.
In the early 1990s, the Derg regime began to lose its control over Ethiopia. The OLF failed to maintain strong alliances with the other two big rebel groups at the time; the Eritrean People's Liberation Front (EPLF) and the Tigrayan People's Liberation Front (TPLF). In 1990, the TPLF created an umbrella organization for several rebel groups in Ethiopia, the Ethiopian People's Revolutionary Democratic Front (EPRDF). The EPRDF's Oromo subordinate, the Oromo Peoples' Democratic Organization (OPDO) was seen as an attempted replacement for the OLF.
In 1991, the EPRDF seized power and established a transitional government. The EPRDF and the OLF pledged to work together in the new government; however, they were largely unable to cooperate, as the OLF saw the OPDO as an EPRDF ploy to limit their influence. In 1992, the OLF announced that it was withdrawing from the transitional government because of "harassment and [the]assassinations of its members". In response, the EPRDF sent soldiers to destroy OLA camps. Despite initial victories against the EPRDF, the OLF were eventually overwhelmed by the EPRDF's superior numbers and weaponry, forcing OLA soldiers to use guerrilla warfare instead of traditional tactics.
In the late 1990s, most of the OLF's leaders had escaped Ethiopia, and the land originally administer by the OLF had been seized by the Ethiopian government, now led by the EPRDF.
After the Eritrean–Ethiopian War, the OLF moved its leadership and headquarters to Eritrea. The OLA allegedly began receiving military training and arms from the Eritrean government. On 25 July 2000, OLF and IFLO signed a peace agreement after five days of negotiations, thus ending 20 years of inter-factional fighting. 
In 2006, the OLA in southern Oromia retreated into Kenya in an attempt to regroup. That same year, Brigadier General Kemel Gelchu of the Ethiopian military took 100 of his soldiers and joined the OLF in Eritrea. Despite initially aiding the OLF as leader of its military wing, in 2008, General Kemel Gelchu took matters into his own hands and announced that the OLF would lay down its weapons and abandon its previous goal of seceding Oromia and instead work as a political party to democratize Ethiopia. Along with this announcement, he commanded OLF soldiers in south Oromia to lay down their weapons and surrender to the government.
On 30 May 2015, various media outlets reported that the OLF had attacked a federal police station in the Ethiopian side of Moyale town killing 12 Ethiopian soldiers. This occurred weeks after Ethiopian forces swarmed across the Kenyan border and began absuing locals of Sololo town looking for OLF troops. These forces later responded to the attack by launching an attack Moyale District Hospital and killing one guard.
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