Hmm, it looks like you deleted this post. I hope you still get to see this answer.

After British Somaliland joined Italian Somaliland to form the Republic of Somalia in 1960, the idea of Greater Somalia was a hugely important question for the Somali state and people, and impacted relations with Kenya and Ethiopia.

Between 1963 and 1967, ethnic Somalis in the Northern Frontier District of Kenya fought to separate themselves from Kenya and join Somalia, supported by the Somali government. This period is known in Kenya as the Shifta War, for the term shifta, which connotes a rebel or a bandit.

The government of Kenya was able to defeat the insurgency of the ethnic Somalis through a policy of forcing ethnic Somali nomadic pastoralists to settle in secure villages so they could be tracked. The conflict essentially ended in 1967, when the governments of Kenya and Somalia signed a ceasefire agreement, and Somali support for the secessionist movement in the Northern Frontier District ended.

This conflict had two major legacies for East African geopolitics. First off, the threat of ethnic somalis waging a secessionist war with support from the Somali Republic led the governments of Kenya and Ethiopia to enter into a bilateral security treaty in 1963.

Secondly, Haile Selassies concerns about the Ogaden region being brought into a Greater Somalia led him to advocate at the Organization for African Unity against redrawing borders of newly independent states. In 1964, the OAU did adopt the Cairo Resolution, which stated a policy that African states would retain the colonial borders, and adjustments to the border between two states could only happen by mutual consent of the two parties.

For its part, Somalia pursued a policy of alignment with the Soviet Union, for which it received a great deal of military aid in the form of tanks, planes, weapons, and military training and advisors. Also, the signing of the cease fire was unpopular in Somalia, and in 1969 the president who signed the ceasefire was assassinated, and a coup brought general Mohamed Siad Barre to power. Soon after taking power, Barre disavowed the agreement.

In 1974, famine in Ethiopia led to the overthrow of Haile Selassie, and eventually to the establishment of a Marxist military junta called the Derg. The chaos of the revolution led to the formation of many rebel groups to fight against the Derg, among the Western Somali Liberation Front, which fought for separation of the Ogaden from Ethiopia and joining with Somalia.

Like in the Shifta war, there is evidence that Somalia was supporting the ethnic Somali rebels. The government of Ethiopia complained that Somalia was sending soldiers across the border to train and fight alongside WSLF rebels. Tensions escalated, and in 1977, the government of Somalia declared war and launched an invasion to try and bring the Ogaden region into Somalia.

Though the Soviet Union and Cuba had been aligned with Somalia since the early 1960s, the Ogaden conflict pitted Soviet-aligned Somalia against an avowedly marxist regime in Ethiopia. The governments of the Soviet Union and Cuba decided that Siad Barre was not a "true marxist" but was only adopting the language of marxism while pursuing nationalist deviations. In effect, they determined that they preferred Ethiopia as an ally, and switched their military support to that side. That switch in support was very important in helping Ethiopia defeat Somalia and keep the Ogaden within Ethiopia.

After the decisive defeat in the Ogaden war, Siad Barre's political position was drastically weakened. In 1978, he managed to put down an abortive coup d'etat, and had many suspected accomplices jailed. Throughout the 1980s, he encountered a growing rebel movement from disaffected clans that wished to topple his government. This movement was eventually successful, and Siad Barre fled the country in 1991.

However, nobody could fill the power vacuum that Siad Barre left behind, and Somalia has endured a long running civil war since 1991.