The introduction of slave soldiers by Badi II has alienated Sennar's ruling dynasty from the Funj warrior aristocracy, which in 1718 deposes the reigning mek and places one of its own ranks on the throne of Sannar.

The mid-eighteenth century witnesses another brief period of expansion when the Funj turn back an Ethiopian invasion, defeat the Fur, and take control of much of Kurdufan, but civil war and the demands of defending the sultanate have overextended the warrior society's resources and sapped its strength.

Another reason for Sannar's decline may have been the growing influence of its hereditary viziers (chancellors), chiefs of a non-Funj tributary tribe who manages court affairs.

The vizier Muhammad Abu al Kaylak, who leads the Funj army in wars in 1761, carries out a palace coup, relegating the sultan to a figurehead role.

Sannar's hold over its vassals diminishes, and by the early nineteenth century more remote areas cease to recognize even the nominal authority of the mek.