The Sēfuwa dynasty seized power in Kānem around 1075, but it was only in the beginning of the thirteenth century that the rulers of Kānem were able to extend their authority over Bornū. Prior to this move small groups of Saharan speakers had already established themselves among the Chadic speakers of the Komadugu Yobe valley. Towards the end of the reign of Dūnama Dībalāmi (c. 1210–48) the court of the Sēfuwa itself was shifted to Bornū, mainly as a result of disturbances in Kānem. Indeed, according to oral traditions of the sixteenth century, the Tubu, in alliance with certain members of the Sēfuwa aristocracy, staged a major rebellion against the central government, apparently attempting to resist the strict application of Islamic principles of government by Dūnama Dībalāmi. Towards the end of the thirteenth century powerful rulers were again able to establish the authority of the Sēfuwa on firm grounds: in the east, even on the fringes of Kānem, they brought the situation under strict control and in the west they extended – or confirmed – the political influence of the Sēfuwa dynasty over the focal points of interregional trade which began to rise in Hausaland. Thus Bornū became the central province of the Sēfuwa Empire in spite of the fact that several kings continued to reside temporarily in the old capital of Djīmī situated in Kānem. This major shift of their territorial basis affected the position of the Sēfuwa in their original homelands. Written sources from the end of the fourteenth century show that the increasing involvement of the Sēfuwa in Bornū and its western border states must have changed their attitude towards the people living east of Lake Chad: after having acquired the character of an autochthonous (or national) dynasty of Kānem – in spite of their foreign origin – the Sēfuwa progressively became an alien power in this major Sudanic state, even though the people of Kānem and Bornū were closely related. Furthermore, the rise of a powerful kingdom in the area of Lake Fitrī under the rule of the Bulāla became a serious threat to the Sēfuwa in their original homelands as the warrior aristocracy of the Bulāla state – which must have been of Kanembu origin – remained closely connected with the sedentary population of Kānem. When finally during the reign of 'Umar b. Idrīs (c. 1382–7), the Sēfuwa were forced by the Bulāla to withdraw their forces from Kānem, this territorial loss did not affect the future development of the Empire to the extent that has formerly been supposed, since losses in the east were largely compensated by earlier gains in the west.
Status of the WEST Travelling Wave Array antenna design and results from the high power mock-up
