Stephen III, King of Croatia

Stephen IV, known as Stephen the Great, was King of Croatia from 1219 until 1253. During this time, he brought the Kingdom of Croatia to its greatest extent, ruling over most of the old Roman provinces of Illyria and Dalmatia.

Stephen unexpectedly succeeded his father, the weak king Petar II after the death of his three elder brothers. Due to the new king's youth and inexperience (he was just sixteen upon taking the throne) he was initially underestimated by his rivals. In 1220, he almost lost his throne due to the revolt of an older cousin, Krešimir. The failure of the revolt, and the bloody treatment of Krešimir that followed did much to consolidate Stephen's rule, and marked him out as a leader to be respected. In 1221, he married the Bulgarian Maria Prienensis, the recently widowed twin sister of Tsar Symeon II, thus drawing himself into the affairs of the Bulgarian kingdom.

Though notionally a vassal of the Roman Emperor at Constantinople, Stephen failed to provide troops to contribute to the war effort against the Jušen in Anatolia in the 1220s and 1230s, and thereafter conducted himself as an independent monarch. He was supported in this by the kings of Hungary and the Parisian Papacy, although Stephen himself never explicitly rejected the doctrines of the Eighth Ecumenical Council. His strategy as a monarch was generally to attempt to steer an independent path to avoid drawing attention from more powerful rivals who generally had their own concerns.

In 1226, Stephen's brother-in-law Symeon II of Bulgaria died young, leaving behind him two young daughters and no male heir. With the Romans increasingly distracted by affairs to the East, Stephen took the opportunity to intervene in Bulgarian politics, marching into Bulgaria to champion the claim of his stepson Ivan, the only child of Maria Prienensis' first husband. The ensuing conflict, known as the War of the Margus after the river system in western Bulgaria, lasted nearly three years, and eventually saw the victory of the Croatian king and his son-in-law, who ruled Bulgaria thereafter as Ivan III. In exchange for his crown, Ivan ceded a large chunk of the western part of the Tsardom to Stephen, who thus gained dominion over a mixed population of Croats, Serbs and Bulgarians.

This great success gave Stephen III a great deal of prestige, and from 1232 onwards he began to claim, on occasion, an imperial title as well as a royal one. The Roman held enclaves of coastal Dalmatia certainly used a style of address towards him hitherto reserved for the monarch of Constantinople, though they stopped short of hailing Stephen as Basileus. In 1236, the Serbs rose up against him, perhaps with Roman support, but the revolt faded away quite quickly: the last Serbian strongholds fell in 1238.

The last decade of Stephen's reign was dominated by increasingly difficult diplomatic relations with the Hungarian monarchy under first Andrew III and then the Croat king's namesake, Stephen II. A surprise Hungarian attack in 1240 pushed back the Croats and seized a number of northern towns, and it would be 1246 before the Hungarians were entirely expelled. A succesful Croat offensive was mounted in 1247, but this failed to gain much ground due to the displeasure of the German Emperor Otto V, a cousin of the Hungarian king.

Despite this, Stephen can be judged to be the most succesful monarch in Croatian history, by some way. Upon his death, he left a full treasury, a strengthened monarchy, and an adult male heir in his son, Petar III. Croatian power would recede after him, but the seeds of decline cannot be attributed to Stephen.