The early history of Medieval Croatian State is mostly unknown. The Frankish sources from the end of the 8th century mention Woinomyrus Sclavus who was according to some scholars a Croatian Duke but the opinions about his origin are greatly divided. History of Medieval Croatian State becomes more clear in the second decade of the 9th century when Prince of Savia, Ljudevit Posavski led a rebellion against the Franks. Croatia was at the time ruled by Prince Borna who joined the Franks against Ljudevit Posavski. The Franks crushed the rebellion in 822, while Ljudevit Posavski escaped in Bosnia and notified the Franks that he was willing to subdue to the emperor. Ljudevit returned to Croatia on the death of Borna in 823 but he was assassinated, probably on Frankish order. The destiny of Slavic principality of Savia afterwards remains unknown but written sources from the end of the 9th century mention Prince Braslav, a loyal German vassal who met with Emperor Arnulf in 892.
Borna’s nephew and heir Vladislav was succeeded by Prince Mislav. More is known about Mislav’s successor Trpimir (c. 845-864) who defeated the Bulgarians and Dalmatian cities and strengthened the Medieval Croatian State. Trpimir was succeeded by Domagoj (c. 864-876) who was not member of the Trpimirovic Dynasty. His reign was marked by increased Byzantine influence and Croatian throne was assumed by Sedeslav/Zdeslav from the Trpimirovic Dynasty with Byzantine help in 878. Sedeslav was succeeded by Branimir (879-892) who turned against the Byzantine Empire and established closer bonds with the Papacy. Branimir reconciled with the Byzantine Empire later, while the Medieval Croatian State developed into an important power on the Adriatic coast.
Branimir was succeeded by Mutimir (892-c.920) of whom very little is known. His successor Tomislav I (c. 910-928) was proclaimed king although is not known when and by whom. However, the Medieval Croatian State fell into inner crisis under Tomislav’s successors Trpimir II, Kresimir I and Miroslav I. A civil war broke out during the reign of Miroslav I (945-949) resulting in rapid switches on the Croatian throne and rise of the local leaders. Raska (Serbia) under Caslav Klonimirovic captured Bosnia, while Stefan Drzislav (d. 997) also felt threatened by Tsar Samuil of Bulgaria. Drzislav joined the Byzantine Emperor Basil II against Tsar Samuil of Bulgaria but his success was short-lasting. Venice stopped paying a tax to the Croatian King for safe sealing in 996, while Drzislav died shortly afterwards.
Drzislav’s death was followed by a war over succession among his three sons Svetoslav, Kresimir III and Gojislav which was taken advantage by the Venetians under Pietro II Orseolo who captured the Croatian lands along the Adriatic Sea. The Croatian crown was eventually assumed by Kresimir III who was forced to subdue to the Byzantine Emperor Basil II who destroyed the Bulgarians under Tsar Samuil. Both Byzantine and Venetian pressure on Kingdom of Croatia (the Byzantine Emperor Basil II died in 1025 and the Orseolo family was expelled from Venice in 1026) ceased in the second decade of the 11th century. However, Kresimir’s successor Stefan I (c. 1030-1058) had to face with the Normans who emerged as an important political force in Southern Italy.
Kingdom of Croatia reached its territorial peak under Kresimir IV (1058-1074). He established his supremacy over Dalmatian cities about 1069 and is titled “rex Dalmatiae atque Croatiae” (king of Dalmatia and Croatia) in all documents which is by some Croatian historians regarded as evidence of Kresimir’s independence from the Byzantine Empire concerning Dalmatia. Kresimir IV was deposed in 1074 and the Croatian throne was assumed by Zvonimir (1075-1089) with the support of Pope Gregory VII. Zvonimir is the first historically proven King of Croatia but little is known about his rule. The majority of the documents is faked and thus Zvonimir’s role in the Byzantine-Norman struggles in the Adriatic remains unknown. He was succeeded by Stjepan II (1089-1091) who was the last King of Croatia of Trpimirovic Dynasty.
Zvonimir’s widow, Jelena who was the sister of Ladislaus I of Hungary refused to recognize Stjepan II as King of Croatia and appealed to the King of Hungary to assume the Croatian throne. The Hungarian attempt failed and king of Croatia became a man named Peter (1092-1097) of whom is known only that he ruled from Knin. However, Ladislaus’ successor Coloman invaded Croatia as soon as he reconciled with the Pope, defeated the Croatian forces in the Battle of Gvozd Mountain in 1097 and killed the last King of Croatia. Coloman was crowned King of Croatia in 1102 and the Kingdom of Croatia was incorporated into the Kingdom of Hungary.