Fortunatus meanwhile was watching events at Istria. Under the sun of Charlemagne’s favours he had waxed rich and powerful. He possessed four ships, and traded under royal patronage wherever the new western Emperor’s power reached. By skilful diplomacy he effected his recall to Grado, and placed a Frankish partizan in the see of Olivolo. But the Heracleans had lost their home, not their ideals and policy. They appealed to the Byzantine Emperor, and a Greek fleet sailed up the Adriatic. Fortunatus once again was a fugitive. The Doge and his party protested a loyalty to their suzerain, which in 809 was translated into acts by the despatch of a fleet to aid him to recover the exarchate for the Greeks. It was unsuccessful, but none the less irritating to the Pope and Emperor, who now determined to subdue the Venetians and incorporate them into the Holy Roman Empire of the West. The immediate cause of the rupture is not known, but when the princes of the earth are bent on war a pretext is seldom hard to find. A great empire, aiming at universal dominion, is ill at ease with a sturdy freedom-loving state on its borders, and the far-reaching arm of the invincible Carlovingians was stretched forth to grasp, as they thought, an easy prey. In the stress of a common danger, faction was silenced. Obelerio and his brother Beato, whom he had associated with him a year after he was proclaimed Doge, advised that the Venetians should agree with their adversary before it was too late, but a wave of popular indignation swept them from power, and Angelo Participazio, a Heraclean by birth, and one of the tribunes of Rivoalto, was made head of a provisional government of national defence. The churches were filled with earnest, determined men, entreating with fasting and prayer the divine aid in their hour of need; a call was made on every citizen at home and abroad to hasten to the defence of the fatherland. Provisions were accumulated, ships built, fortifications raised, channels blocked by chains and sunken hulks, guide posts drawn. [Illustration: CLOISTERS OF S. GREGORIO] Meanwhile, King Pepin had summoned his allies, and a fleet sailed up to the lagoons. On the mainland the advance of the Frankish armies was irresistible; north and south they closed in on the Venetians. Grado soon fell; Brondolo, the Chioggie, and other cities were captured; fire and sword wasted their settlements. The _porti_ of Brondolo, Chioggia, and Pelestrina were forced, Malamocco[6] the capital threatened. At this crisis the momentous decision was taken to abandon Malamocco and concentrate at Rivoalto (Rialto), the compact group of islands between the mainland and the _lidi_. [Illustration: FISHING BOATS]