Early Middle Ages in Venice
The successors of Obelerio inherited a united Venice. By the Pax Nicephori (803), the two emperors had recognised Venetian de facto independence, while it remained nominally Byzantine in subservience. During the reign of the Participazio, Venice grew into its modern form. Though Heraclean by birth, Agnello, first doge of the family, was an early immigrant to Rialto and his doge ship was marked by the expansion of Venice towards the sea via the construction of bridges, canals, bulwarks, fortifications, and stone buildings. The modern Venice, at one with the sea, was being born. Agnello was succeeded by his son Giustiniano, who brought the body of Saint Mark the Evangelist to Venice from Alexandria and made him the patron saint of Venice.
Exterior fresco at Basilica di San Marco
During the reign of the successor of the Participazio, Pietro Tradonico, Venice began to establish its military might which would influence many a later crusade and dominate the Adriatic for centuries, and signed a trade agreement with the Holy Roman Emperor Lothair I, whose privileges were later expanded by Otto I. Tradonico secured the sea by fighting Slavic and Saracen pirates. Tradonico’s reign was long and successful (837 – 864), but he was succeeded by the Participazio and it appeared that a dynasty may have finally been established. Around 841, the Republic of Venice sent a fleet of 60 galleys (each carrying 200 men) to assist the Byzantines in driving the Arabs from Crotone; but failed.
Under Pietro II Candiano Istrian cities signed a treaty under which it accepted the Venetian economical supremacy: it was the first move towards the creation of the coastal empire in Dalmatia. The autocratic, philo-Imperial Candiano dynasty was overthrown by a revolt in 972, and the populace elected doge Pietro I Orseolo; however, his conciliating policy was ineffective, and he resigned in favour of Vitale Candiano. Starting from Pietro II Orseolo, who reigned from 991, attention towards mainland was definitely overshadowed by a strong push towards the control of 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 taxation paid by other foreigners and the Byzantines themselves. In the year 1000 an expedition of 6 ships in Istria secured the Venetian suzerainty in the area, and Slav pirates were suppressed permanently.
In the occasion Orseolo named himself “Duke of Dalmatia”, starting the colonial empire of Venice. He died in 1008; he was also responsible of the establishment of the “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, and had assumed a firm role of balance power between the two major 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 also skilfully intervened in the war between the Normans of Apulia and the Byzantine Emperor Alexios I Komnenos in favour of the latter, obtaining in exchange a bull declaring the Venetian supremacy in the Adriatic coast up to Durazzo, as well as the exemption from taxes for his merchants in the whole Byzantine Empire, a considerable factor in the city-state’s later accumulation of wealth and power serving as middlemen for the lucrative spice and silk trade that funnelled through the Levant and Egypt along the ancient Kingdom of Axum and Roman-Indian routes via the Red Sea.
The war was not a military success, but with that act the city gained total independence of Venice also from the formal point of view. In 1084, Domenico Selvo had personally led a fleet against the Normans, but he was defeated and lost 9 great galleys, the largest and most heavily armed ships in the Venetian war fleet.