There are two major versions of how the Somali people came into possession of their current territory. Some oral-historical evidence suggests that Somalis gradually spread from the north of the country toward the west and, pushing Oromo and Bantu peoples ahead of them, appeared in the south only during the last millennium. According to another version that possibly relates to movements of a much earlier date, the "Sam"-language speakers first emerged east of Lake Turkana in Kenya. Proto-Somali speakers spread to the northeast from the Tana River and into the Somali Peninsula. Neither of the versions can draw support from archaeological finds. There is evidence that two northern port towns, Zeila and Berbera, were already flourishing in 100 B . C . During the first half of the current millennium, the coastal settlements along the southern shore, in the Benadir region, became established as important commercial centers, with trade networks extending along substantial parts of the East African coast and into the interior of the Horn. During the nineteenth century, Benadir ports came under the dominion of the Omani sultanate, and southern Somali agriculture received an influx of imported slave labor. In the late nineteenth century southern Somalia became an Italian colony; the northern part of country was colonized by the British. After the Italians were defeated during World War II, they were granted their former colony in United Nations trusteeship from 1950 until the independence and unification of the two former colonies in 1960. The frail parliamentary democracy that was installed was overthrown in a 1969 coup d'état that brought Major General Mohammed Siad Barre to power. During some two decades of military rule, the Soviet Union and the United States succeeded one another as Somalia's chief ally. In 1977-1978 Somalia sought unsuccessfully to take from Ethiopia the Ogaden region, which is inhabited primarily by ethnic Somalis. The final resolution of that conflict was not reached until the spring of 1988. In the late 1980s a bloody civil war between Somali government troops and several resistance groups led to a mass exodus of at least 400,000 northern Somalis to Ethiopia.