As the power of the Byzantine Empire dwindled in northern Italy in the late 7th century, the lagoon communities came together for mutual defence against the Lombards, as the Duchy of Venetia. The Duchy included the patriarchates of Aquileia and Grado, in modern Friuli, by the Lagoon of Grado and Carole, east of that of Venice. Ravenna and the duchy were connected only by sea routes, and with the duchy's isolated position came increasing autonomy. The "tribuni maiores" formed the earliest central standing governing committee of the islands in the lagoon - traditionally dated to c. 568.