power, took the throne and became the first King of a reunified Poland. His son, Casimir III, is remembered as one of the greatest Polish kings, who was widely recognized as a protector of trade. He extended his kingdom to 250% of its initial size. Casimir is also known for extending royal protection to Jews and providing the original impetus for the establishment of Poland's first university. The Golden Liberty of the nobles began to develop under Casimir's rule, when in return for their military support, the king made serious concessions to the aristocrats, finally establishing their status as superior to that of the townsmen, and aiding their rise to power. When Casimir died in 1370 he left no legitimate male heir and, considering his other male descendants either too young or unsuitable, was laid to rest as the last of the nation's Piast rulers.
Poland was also a centre of migration of peoples. The Germans settled in the towns, the Jewish community began to settle and flourish in Poland during this era (see History of the Jews in Poland); the same applies in smaller number to Armenians. The Black Death which affected most parts of Europe from 1347 to 1351 affected Poland to lesser extent.
Jagiellon dynasty
The rule of the Jagiellon dynasty spanned the late Middle Ages and early Modern Era of Polish history. Beginning with the Lithuanian Grand Duke Jogaila (Władysław II Jagiełło), the Jagiellon dynasty (1386–1572) formed the Polish–Lithuanian union. The partnership brought vast Lithuania-controlled Rus' areas into Poland's sphere of influence and proved beneficial for the Poles and Lithuanians, who coexisted and cooperated in one of the largest political entities in Europe for the next four centuries. In the Baltic Sea region Poland's struggle with the Teutonic Knights continued and included the Battle of Grunwald (1410), where a Polish-Lithuanian army inflicted a decisive defeat on the Teutonic Knights, both countries' main
