Albania converted and a great number of Albanian clerics and monks were present in the Dalmatian Catholic institutions. Around 1230 the two main centers of Albanian settlements were around Devoll river in what is now central Albania and the other around the region known as Arbanon. Albanian presence in Croatia can be traced back to the beginning of the Late Middle Ages. In this period, there was a significant Albanian community in Ragusa with a number of families of Albanian origin inclusively the Sorgo family who came from the Cape of Rodon in central Albania, across Kotor in eastern Montenegro, to Dalmatia. By the 13th century, Albanian merchants were trading directly with the peoples of the Republic of Ragusa in Dalmatia which increased familiarity between Albanians and Ragusans. The upcoming invasion of Albania by the Ottoman Empire and the death of Skanderbeg caused many Christian Albanians to flee to Dalmatia and surrounding countries. In the 14th century a number of Albanian principalities were created. These included Principality of Kastrioti, Principality of Dukagjini, Princedom of Albania, and Principality of Gjirokastër. At the beginning of the 15th century these principalities became stronger, especially because of the fall of the Serbian Empire. Some of these principalities were united in 1444 under the anti-Ottoman military alliance called League of Lezha. Albanians were recruited all over Europe as a light cavalry known as stratioti. The stratioti were pioneers of light cavalry tactics during the 15th century. In the early 16th century heavy cavalry in the European armies was principally remodeled after Albanian stradioti of the Venetian army, Hungarian hussars and German mercenary cavalry units (Schwarzreitern). Ottoman Empire Prior to the Ottoman conquest of Albania, the political situation of the Albanian people was characterised by a fragmented conglomeration of scattered kingdoms and principalities such as the Principalities of Arbanon, Kastrioti and Thopia. Before and after the fall of Constantinople, the Ottoman Empire continued an extended period of conquest and expansion with its borders going deep into the Southeast Europe. As a consequence thousands of Albanians from Albania, Epirus and Peloponnese escaped to Calabria, Naples, Ragusa and Sicily, whereby others sought protection at the often inaccessible Mountains of Albania. Under the leadership of Gjergj Kastrioti Skanderbeg, a former governor of the Ottoman Sanjak of Dibra, a prosperous and longstanding revolution erupted with the formation of the League of Lezhë in 1444 up until the Siege of Shkodër