the shari river formed the kingdom's western boundary, with most of its interior watered by its effluents. the area was home to a kind of footworm that mutilated many of the inhabitants. bagirmi was also continually plagued by drought, pestilence, and slave raiding both internally and externally organized. during the reign of idris alooma bornu conquered bagirmi. the muslim bagirmi would raid the pagan tribes of their own kingdom in order to pay the necessary tribute to bornu. except of slaves, including eunuchs, bagirmi also exported animal skins, ivory and cotton, while importing copper and cowrie shells. trade with bornu was carried out by caravans along a route which extended north across the sahara to tripoli on the libyan coast. during the reign of mbang muhammad al-amin (r. 1751-1785) bagirmi became independent again, although the tributary status remained.