But once fortified within the ramparts of Byzantium the Franks enjoyed the inestimable advantage which their Greek predecessors had possessed: they were masters of a fortress which—as military science then stood—was practically impregnable, if only it was defended with ordinary skill, and adequately guarded on the front facing the sea. As long as the Venetians kept up their naval supremacy in Eastern waters, the city was safe on that side, and even the very limited force which the Latin emperor could put into the field sufficed, when joined to the armed burghers of the Italian quarters, to defend the tremendous land wall. From the first year of its existence the Latin Empire was marked out by unfailing signs as a power not destined to continue. The intention of its founders had been to replace the centralized despotism which they had overthrown by a great feudal state, corresponding in territorial extent to its predecessor. But within a few months it became evident that the conquest of the broad provinces which the Crusaders had distributed among themselves by anticipation, was not to be carried out. The new emperor himself was the first to discover this. He set out with his chivalry to drive from Northern Thrace the Bulgarian hordes, who had flocked down into the plains to profit by the plunder of the dismembered realm. But near Adrianople he met Joannicios, the Bulgarian king, with a vast army at his back. The Franks charged gallantly enough, but they were simply overwhelmed by numbers. The larger part of the army was cut to pieces, and Baldwin himself was taken prisoner. The Bulgarian kept him in chains for some months, and then put him to death, after he had worn the imperial crown only one year [1205]. Henry of Flanders, the brother of Baldwin, became his successor. He was an honest and able man, but he could do nothing towards conquering the provinces of Asia, pushing the Bulgarians back over the Balkans, or conciliating the subject Greek population. All his reign he had to fight on the defensive against his neighbours to the north and south. By the time that he died the empire was practically confined to a narrow slip of land along the Propontis, reaching from Gallipoli to Constantinople. Nor was the chief of the minor Latin states any better off; Boniface of Montferrat had fallen in 1207, slain in battle by the same Bulgarian hordes which had cut off the army of his suzerain Baldwin. With his death it became evident that the kingdom of Thessalonica was no more able to conquer all the old Byzantine provinces in its neighbourhood than was the empire of Constantinople. Boniface’s son and heir was a mere infant; during his minority the lands of his kingdom were lopped away, one after another, by the Greek despot of Epirus, the able Theodore Angelus. At last the capital itself was retaken by the Greeks in 1222, and the kingdom of Thessalonica came to an end.