Beginning with Doge Pietro II Orseolo, who ruled Venice from 991 AD, Venetian attention towards mainland Veneto was definitely overshadowed by a strong push towards the control of the Adriatic Sea. Inner strife was pacified, and trade with the Byzantine Empire boosted by the favourable treaty (Grisobolus or Golden Bull) with Emperor Basil II. The imperial edict granted Venetian traders freedom from the Kommerkion tax paid by other foreigners and the Byzantines themselves. In 1000 AD an expedition of Venetian ships in coastal Istria and Dalmatia secured Venetian suzerainty in the area, and the Narentine pirates were suppressed permanently. On this occasion Doge Orseolo named himself "Duke of Dalmatia", starting the colonial empire of Venice. He was also responsible of the establishment of the famous "Marriage of the Sea" ceremony. At this time Venice had a firm control over the Adriatic Sea, strengthened by the expedition of Pietro's son Ottone in 1017.
