Much of Bosnia is taken over after the death of Tomislav in 928 by a Serb princedom that acknowledges the sovereignty of Constantinople.

The first recorded mention of Bosnia is written during this period by the the Greek emperor Constantine VII Porphyrogenitus, whose writings are one of the best sources of information on the Greek empire and neighboring areas.

Describing “Bosona” as a district in “baptized Serbia,” the district he refers to is an area much smaller than modern Bosnia and centered on the Bosna River.

Soon after Constantine writes those words, most of the modern territory of Bosnia reverts to Croatian rule.