Pope was duke Branimir, whom Pope John VIII referred to as Dux Croatorum ("Duke of Croats") in 879.
Tomislav was the first ruler of Croatia who was styled a king in a letter from the Pope John X, dating kingdom of Croatia to year 925. Tomislav defeated Hungarian and Bulgarian invasions, spreading the influence of Croatian kings. The medieval Croatian kingdom reached its peak in the 11th century during the reigns of Petar Krešimir IV (1058–1074) and Dmitar Zvonimir (1075–1089). When Stjepan II died in 1091 ending the Trpimirović dynasty, Ladislaus I of Hungary claimed Croatian crown. Opposition to the claim led to a war and personal union of Croatia and Hungary in 1102, ruled by Coloman.
For the next four centuries, the Kingdom of Croatia was ruled by the Sabor (parliament) and a Ban (viceroy) appointed by the king. The period saw increasing threat of Ottoman conquest and struggle against the Republic of Venice for control of coastal areas. The Venetians gained control over most of Dalmatia by 1428, with exception of the city-state of Dubrovnik which became independent. Ottoman conquests led to the 1493 Battle of Krbava field and 1526 Battle of Mohács, both ending in decisive Ottoman victories. King Louis II died at Mohács, and in 1527, the Parliament on Cetin chose Ferdinand I of the House of Habsburg as new ruler of Croatia, under the condition that he provide protection to Croatia against the Ottoman Empire while respecting its political rights. The period saw rise of native nobility such as the Frankopans and the Šubićs to prominence and ultimately numerous Bans from the two families. In practice Croatia was a free and independent kingdom only from 910 till 1102.
Habsburg Monarchy and Austria-Hungary
Following the decisive Ottoman victories, Croatia was split into civilian and military territories, with the partition formed in 1538. The military territories would become known as the Croatian Military Frontier and were
