Under these circumstances, Thessalonica and Dyrrhachium became points of great consequence to the empire, and were successfully defended by the emperor amidst all his calamities. These two cities commanded the extremities of the usual road between Constantinople and Ravenna, and connected the towns on the Archipelago with the Adriatic and with Rome. The open country was abandoned to the Avars and Slavonians, who were allowed to effect permanent settlements even to the south of the Via Egnatia; but none of these settlements were suffered to interfere with the lines of communication, without which the imperial influence in Italy would have been soon annihilated, and the trade of the West lost to the Greeks. The ambition of the barbarians was inclined to dare any attempt to encroach on the wealth of the Eastern Empire, and they tried to establish a system of maritime depredations in the Archipelago; but Heraclius was able to frustrate their schemes, though it is probable that he owed his success more to the exertions of the mercantile population of the Greek cities than to the exploits of his own troops. National distinctions and religious interests tended to divide the population, and to balance political power, much more in Italy than in the other countries of Europe. The influence of the church in protecting the people, the weakness of the Lombard sovereigns, from the small numerical strength of the Lombard population, and the oppressive fiscal government of the Roman exarchs, gave the Italians the means of creating a national existence, amidst the conflicts of their masters. Yet so imperfect was the unity of interests, or so great were the difficulties of communication between the people of various parts of Italy, that the imperial authority not only defended its own dominions with success against foreign enemies, but also repressed with ease the ambitious or patriotic attempts of the popes to acquire political power, and punished equally the seditions of the people and the rebellions of the chiefs, who, like Joannes Compsa of Neapolis and the exarch Eleutherinus, aspired at independence.