Following the death of Simeon I of Bulgaria, Byzantium no longer needed Croatia's military support and repealed its alliance. Previously, Byzantium relied heavily on the Croats to threaten Symeon from the west. Despite the achievements of King Tomislav in halting Bulgaria's expansion, Byzantium reversed Croatia's supremacy over the Theme of Dalmatia, which fell once again under its administration. However, Byzantine administration was nominal.
Trpimir's woes did not stop there. Pope Leo VI abolished the Diocese of Nin in 928 and transferred Bishop Grgur to Skradin, in what was seen as a humiliating defeat for pro-Slavic proponents in the long running dispute between the Split and Nin Bishoprics.
Dzino, Danijel (2010). Becoming Slav, Becoming Croat: Identity Transformations in Post-Roman and Early Medieval Dalmatia. Brill. ISBN978-90-04-18646-0.
Fine (Jr), John V. A. (2006). When Ethnicity Did Not Matter in the Balkans: A Study of Identity in Pre-Nationalist Croatia, Dalmatia, and Slavonia in the Medieval and Early-Modern Periods. Ann Arbor: University of Michigan Press. ISBN978-0-472-11414-6.