With this distribution of peoples in the 10th century, the stage was set for the great movements of expansion of the Somali toward the south and of the Oromo to the south and west. The first known major impetus to Somali migration was that of Sheikh Ismāʿīl Jabartī, ancestor of the Daarood Somali, who apparently traveled from Arabia to settle in the northeastern corner of the Somali peninsula in the 11th century. This was followed, perhaps two centuries later, by the settlement of Sheikh Isaq, founder of the Isaaq Somali. As the Daarood and Isaaq clans grew in numbers and territory in the northeast, they began to vie with their Oromo neighbours, thus creating a general thrust toward the southwest. By the 16th century the movements that followed seem to have established much of the present distribution of Somali clans in northern Somalia. Other Somali pressed farther south, and some, according to the Arab geographer Ibn Saʿīd, had already reached the region of Marca by as early as the 13th century.

In the meantime, farther to the west a ring of militant Muslim sultanates had grown up around the Christian kingdom of Ethiopia, and the two sides were engaged in a protracted struggle for supremacy. Somali clansmen regularly formed part of the Muslim armies: the name Somali first occurs in an Ethiopian song of victory early in the 15th century. In the 16th century the Muslim state of Adal, whose port was Seylac, assumed the lead in the holy wars against the Christian Amhara. The turning point in the struggle between Christians and Muslims was reached with the Ethiopian victory in 1542, with Portuguese support, over the remarkable Muslim leader Aḥmad ibn Ibrāhīm al-Ghāzī (known to the Ethiopians as Aḥmad GrāŃ). With his Somali armies, Aḥmad had harried Ethiopia almost to the point of collapse. This victory, which saved Ethiopia, also closed the door to Somali expansion westward and increased the pressure of the Somali and Oromo thrust southward. With this stimulus the main mass of the Oromo swept into Ethiopia from the south and southwest and streamed in conquering hordes as far north as the ancient city of Hārer.

This massive invasion left something of a political vacuum in the south of the Horn, which new Somali settlers were quick to fill. By the 17th century the influx of new migrants, competing and jostling with each other, had become considerable. The old Ajuran Somali sultanate, linked with the port of Mogadishu, was overthrown, and Mogadishu itself was invaded and split into two rival quarters. Some of the earlier Somali groups found refuge in northern Kenya. The continuing Somali thrust south—largely at the expense of Oromo and Zanj predecessors—was ultimately effectively halted at the Tana River only by the establishment of administrative posts in about 1912.

Somali clans and foreign traders

Thus, by the latter part of the 19th century, the coastal and hinterland traditions had merged, and the centre of pressure had swung from the coast to the interior. In the north the ancient ports of Berbera and Seylac, much reduced in prosperity and importance, were now controlled by Somali nomads, and the position of the old ports of Marca, Baraawe, and Mogadishu was very similar. These towns had all been penetrated by various Somali clans, and the dominant political influence became that exercised by the Geledi clan ruling the lower reaches of the Shabeelle. Commercial and political links that provided an opening for European infiltration had, however, also been forged between these two coasts and the outside world. Part of the northern Somali coast, including Seylac, was then nominally under Turkish suzerainty (the Turkish claim going back to the 16th century, when Turkish forces had aided Aḥmad Grāñ in his campaigns against Ethiopia). The southern coastal towns, on the other hand, acknowledged the overlordship of the sultan of Zanzibar, although the latter’s authority was slight in comparison with that exercised locally by the Geledi Somali.

Competition between the European powers and Ethiopia

About the middle of the 19th century, the Somali peninsula became a theatre of competition between Great Britain, Italy, and France. On the African continent itself Egypt also was involved, and later Ethiopia, expanding and consolidating its realm under the guiding leadership of the emperors Tewodros II, Yohannes IV, and Menilek II. Britain’s interest in the northern Somali coast followed the establishment in 1839 of the British coaling station at Aden on the short route to India. The Aden garrison relied upon the importation of meat from the adjacent Somali coast. France sought its own coaling station and obtained Obock on the Afar coast in 1862, later thrusting eastward and developing the Somali port of Djibouti. Farther north, Italy opened a station in 1869 at Aseb, which, with later acquisitions, became the colony of Eritrea. Stimulated by these European maneuvers, Egypt revived Turkey’s ancient claims to the Red Sea coast. In 1870 the Egyptian flag was raised at Bullaxaar (Bulhar) and at Berbera.

Britain at first protested these Egyptian moves but by 1877 had come to regard the Egyptian occupation as a convenient bulwark against the encroachments of European rivals. With the disorganization caused by the revolt in the Sudan during this period, however, Egypt was obliged to curtail its colonial responsibilities, evacuating Hārer and its Somali possessions in 1885. In these circumstances the British government reluctantly decided to fill the gap left by Egypt. Between 1884 and 1886, accordingly, treaties of protection were drawn up with the main northern Somali clans guaranteeing them their “independence.” Somali territory was not fully ceded to Britain, but a British protectorate was proclaimed and vice-consuls appointed to maintain order and control trade at Seylac, Berbera, and Bullaxaar. The interior of the country was left undisturbed, only the coast being affected.

Meanwhile, France had been assiduously extending its colony from Obock, and a clash with Britain was only narrowly averted when an Anglo-French agreement on the boundaries of the two powers’ Somali possessions was signed in 1888. In the same period, the Italians were also actively extending their Eritrean colony and encroaching upon Ethiopian territory. Not to be outdone, Menilek took the opportunity of seizing the Muslim city of Hārer, left independent after the Egyptian withdrawal. In 1889 Ethiopia and Italy concluded the Treaty of Wichale, which in the Italian view established an Italian protectorate over Ethiopia. Arms and capital were poured into the country, and Menilek was able to apply these new resources to bring pressure to bear on the Somali clansmen around Hārer. In 1889 Italy also acquired two protectorates in the northeastern corner of Somalia, and by the end of the year the southern part of the Somali coast leased by the British East Africa Company from the sultan of Zanzibar was sublet to an Italian company.

Italy had thus acquired a Somali colony. From 1892 the lease was held directly from Zanzibar for an annual rent of 160,000 rupees, and, after the failure of two Italian companies by 1905, the Italian government assumed direct responsibility for its colony of Italian Somaliland. To the south of the Jubba River the British East Africa Company held Jubaland until 1895, when this became part of Britain’s East Africa protectorate. Britain and Italy had reached agreement in 1884 on the extent of their respective Somali territories, but the Battle of Adwa (1896), at which the infiltrating Italian armies were crushed by Ethiopian forces, radically changed the position. Ethiopia, then independent of Italy, was plainly master of the hinterland, and in 1896–97 Italy, France, and Britain all signed treaties with Emperor Menilek, curtailing their Somali possessions. Italy gave up the Somali Ogaden, and Britain excised much of the western Hawd from its protectorate. Although the land and the Somali clansmen (who were not consulted), so abandoned, were not recognized as belonging to Ethiopia, there was nothing then to stop their gradual acquisition by Ethiopia.