At the peak of their power, Omis Pirates were one of the most powerful and fearsome pirates on the whole Mediterranean Sea. In the 12. and 13. century Omis was governed by the dukes Kacics, the leaders of the pirates of Omis. The Omis dukes from the Kacic family: Malduk, Toljen, Pribislav, Osor were the masters of the Adriatic Sea, so mighty that the towns of Dubrovnik and Kotor were forced to make treaties with them on non-attacking, and in the 13 th century even Venice appeared as a party in the pact with the Omis pirates making a commitment to pay tribute to ensure free sailing and trade. The pirates of Omis used to attack Pope's galleys and merchants of Venetia, Dubrovnik, Kotor, Split. On few occasions they even attacked the crusaders on their way to the Holy Land.
Omis Pirates ruled the Adriatic Sea for more then three centuries until in the year of 1420 the whole of Dalmatia, except Omis, fell under rule the of Venetian Republic, the most powerful naval force of those times. Surrounded by the enemy and left completely alone, the Pirates of Omis managed to defend themselves for 24 years. In 1444, Omis fell into the hands of Venetia and that year marks the end of piracy on Adriatic Sea.
Omis Pirates were extraordinary sailors and shipbuilders, famous for their Sagittas (the Arrow), a special type of ship constructed for fast attack and even faster retrieval into the safety of the mouth of the Cetina River. Due to its position and the bravery of its inhabitants, Omis was practically impregnable to all invaders. Even the Turks, who conquered all of the south-eastern Europe, and were stopped at the gates of Vienna, didn't manage to defeat Omis.
- 1145. Povlja, Island Brac - Benedictine monastery, built between the end of the 9th and the beginning of the 10th century, was devastated in 1145 by pirates of Omis.
- 1167. Duke Nikola Kacic signs peace treaty with the merchants of Kotor. The treaty was soon broken.
- 1180. Archbishop Arnir of Constantinople gets stoned to death in Omis.
- 1190. Kacics signs treaty with Dubrovnik. This treaty was also soon broken.
- 1200. Komiza, Island Vis - The Benedictines moved their monastery from Bisevo to Saint Nicholas Church in Komiza due to the threat of attack by the Omis pirates.
- 1208. Venice makes pact with the Omis pirates making a commitment to pay tribute to ensure free sailing and trade.
- 1220. The Pirates of Omis attacked the Pope's crusaders on their way to Palestine.
- 1221. Pope Honorius III undertook crusade against Omis pirates. Pirates won the war.
- 1226. Duke Toljen Kacic pillages the surrounding of Split.
- 1228. Pope Honorius III undertook another crusade against Omis pirates. Pirates lost the war, but the piracy continued.
- 1228. Splitska, Island Brac - The church of St. Maria was destroyed by the Pirates of Omis.
- 1236. Venetia and Dubrovnik form an alliance against the Pirates of Omis.
- 1241. Island Solta - The islands churches, as well as the island villages were badly damaged when the Duke of Omis, Osor Kacic and his pirates invaded the island.
- 1273. The Pirates of Omiš robbed Henry, Bishop of Kefalonia.
- 1277. Nerezisca, Island Brac - This year is known in Nerezisca for the Omis Pirates attack: they set the Brac office building on fire and destroyed the Brac archives.
- 1278. Island Brac was captured for the first time by Pirates of Omis.
- 1280. Sucuraj, Island Hvar - Monastery of the hermit brothers of St. Augustine, was burnt dovn in by Omis pirates.
- 1294. Povlja, Island Brac - The Pirates of Omis pillaged Povlja monastery again.
- 1331. Island Hvar - After several centuries in which Venice, Byzantium and Croat-Hungarian kings ruled the island; in 1331 it opted for the most powerful of the lot – Venice – as a protection against the notorious pirates of Omis.
