Complex sentence: In 1537, while the Venetians still reigned, Mykonos was attacked by Barbarossa, the infamous admiral of Suleiman the Magnificent, and an Ottoman fleet established itself on the island.
Split into simpler sentences: In 1537, while the Venetians still reigned, Mykonos was attacked by Barbarossa, an admiral of Suleiman the Magnificent. An Ottoman fleet established itself on the island.