whose trade and traffic followed the commercial routes to the north and northwest, with Hamburg as the main port for Austrian products. When these routes became vulnerable to the growing Prussian state, the monarchy started to turn towards its southern possessions. The trade of Fiume still languished, since the Habsburgs favored Trieste for all Austrian exports, also because land communications thorough Fiume were insecure. From 1469 to 1502, Turkish attacks in Croatia and the environs of Fiume were particularly frequent, with the near absence of any organised defence. The threat from the Ottoman Empire kept the monarchy engaged in permanent military actions and in concluding alliances with Christian states, with Venice being one of them. The northern Adriatic thus functioned as an Ottoman, Venetian, and Habsburg borderland. For centuries, the regional border was indistinct and mobile: the Croatian littoral and its hinterland were an integrated part of the Habsburg military frontier, which was more than defensive; and whose military nature marked the stages of societal development in the area. Its principal characteristic was that the various fortresses were manned by regular and irregular troops for permanent, low-intensity warfare, which included raiding as its main source of revenue. Incursions of armed bands—from the Ottoman side, the irregular Hajduks and Uskoks, as well as the local frontier troops (Grenzers)—occurred on a daily basis. Probably no phenomenon describes the turbulent events in the area better than the Uskoks' piracy and banditry in the northern Adriatic. For a century, Uskoks served as irregulars in the Habsburg border garrison of Senj. The Habsburgs and the Pope celebrated the irregulars' role as a bulwark of Christendom, while for the Venetians (laity and priests alike) they were "bandits and pirates worse than the Turks and responsible for innumerable atrocities". For much of the 16th century, Fiume's history is very much that of the Uskoks. In fact, the city survived as a port of trade principally thanks to the afflux of the merchandise they pillaged. It was a world where life was precarious and trade degenerated into a raiding economy. In 1530, Venice, knowing that the Uskoks had Fiume as their main "emporium", sacked and burned the city during a punitive expedition. Uskok piracy became a serious diplomatic problem between Austria and Venice, which was resolved in 1617 with the Treaty of Madrid, by which the emperor discontinued his support of the Uskoks. The repeated attempts of Habsburg