Zaharije, who has been persuaded by Constantinople to revolt against Simeon, is supported by many Bulgarians exhausted from Simeon's endless campaigns against the Empire.
The Bulgarian emperor sends a punitive force under Sigrica and Marmais, but they are routed and the two commanders beheaded, which forces Simeon to conclude an armistice with Constantinople in order to concentrate on the suppression of the uprising.
Simeon sends an army led by Časlav Klonimirović in 924 to depose Zaharije.
He is successful, as Zaharije flees to Croatia.
The Serbian zhupans are then summoned to recognize Caslav as the new Prince.
When they come, however, they are all imprisoned and taken to Bulgaria, as is Časlav.
Much of Serbia is ravaged, and many people flee to Croatia, Bulgaria and Constantinople.
Simeon makes Serbia into a Bulgarian province, so that Bulgaria now borders Croatia and Zahumlje.
He then resolves to attack Croatia, because it is an ally of the Empire and had sheltered the Serbian prince.