History of the Republic of Venice of the Sea" ceremony was established in this period. Orseolo died in 1008. Venice's control over the Adriatic was strengthened by an expedition by Pietro's son Ottone in 1017, by which time Venice had assumed a key role in balancing power between the Byzantine and Holy Roman Empires. During the long Investiture Controversy, an 11th-century dispute between Henry IV, Holy Roman Emperor and Pope Gregory VII over who would control appointments of church officials, Venice remained neutral, and this caused some attrition of support from the Popes. Doge Domenico Selvo intervened in the war between the Normans of Apulia and
History of the Republic of Venice captured and sacked in 1204. Venetians saved from the sack several artistic works, such as the famous four bronze horses, bringing them to Venice. As a result of the partition of the Byzantine Empire that followed, Venice gained some strategic territories in the Aegean Sea (three-eighths of the Byzantine Empire), including the islands of Crete and Euboea. Moreover, some present day cities, such as Chania on Crete, have core architecture that is substantially Venetian in origin. The Aegean islands formed the Venetian Duchy of the Archipelago. The Republic of Venice signed a trade treaty with the Mongol Empire in 1221.