To the east, the Kanem–Bornu Empire dominated the region around Lake Chad for much of this period. It was founded by the Zaghawa around the 8th century and based in Njimi, north-east of the lake. The kingdom gradually expanded, especially during the rule of the Sayfawa Dynasty which began in c. 1075 under ''Mai'' (king) Hummay. The kingdom reached its greatest extent in the 1200s, largely thanks to the effort of ''Mai'' Dunama Dibbalemi (r. 1210–1259), and grew rich from its control of many Trans-Saharan trade routes; much of eastern and south-eastern Niger, notably Bilma and Kaouar, was under Kanem's control in this period. Islam had been introduced to the kingdom by Arab traders from the 11th century, gradually gaining more converts over the following centuries. Attacks by the Bulala people in the late 14th century forced Kanem to shift westwards of Lake Chad, where it became known as the Bornu Empire, ruled from its capital Ngazargamu on the modern Niger-Nigeria border. Bornu prospered during the rule of ''Mai'' Idris Alooma (r. circa 1575–1610) and re-conquered much of the traditional lands of Kanem, hence the designation 'Kanem–Bornu' for the empire. By the late 17th century and into the 18th the Bornu kingdom had entered a long period of decline, gradually shrinking back to its Lake Chad heartland, though it remained an important player in the region.