Casimir was undoubtedly one of the greatest kings of Poland. When he ascended the throne in 1333, Poland was only a conglomeration of two provinces, Greater and Lesser Poland, together with the lands of Cuiavia, Łęczyca, Sieradz and Sandomierz. This was a result of the fragmentation instituted in 1138 by Boleslaus the Wry-Mouthed, who wanted to forestall dynastic feuds over the succession. Two centuries of division and conflict, finally ended by the successful endeavour made by Casimir's father, Vladislaus the Ell-High, to re-unite the kingdom, had turned Poland, formerly esteemed throughout Europe, into a weak country, with only a marginal role on the international political scene. The young Casimir was faced with the daunting task of restoring his kingdom to its erstwhile glory by continuing his father's work: reclaiming lost provinces, filling the empty treasury and ensuring peace and prosperity for his subjects.
Casimir's task was difficult; the progress made in the late Middle Ages had by-passed Poland and left its people behind western Europe. In addition there were the financial problems and unpopular but unavoidable political decisions, which kindled the hostility of numerous magnates to Casimir both within Poland and outside its borders . Nonetheless, he managed in a short time to put the country back on its feet, remedying domestic problems and entering treaties and agreements with neighbouring countries which helped him to retrieve part of the forfeited territories. He also managed to acquire the Duchy of Halicz in Ruthenia (Rus').
Thanks to these territorial accessions, Poland and her inhabitants began to change. The people represented a number of cultures and religions, the outcome of which was the prevalence of a social attitude of religious tolerance, a necessary prerequisite to ensure that various communities could live in peace alongside each other in dominions which were gradually expanding to become one of the vastest realms in Europe. Thanks to the spirit of tolerance Poland enjoyed an influx of Italians, Jews, Flemish people, Wallachians, Germans, Englishmen and Scots, Frenchmen and several other groups. The most convenient East-West trading route, which passed through the Polish territories, greatly stimulated the development of trade, agriculture, mining and the crafts, which in turn significantly raised the standard of living of Poland's inhabitants. The towns which had been devastated were rebuilt and the royal treasury filled up. Casimir codified the law and carried out monetary and military reform, thanks to which the Polish army became a significant force in Europe. The king built up a reputation as a good master. His wise policy gained him the favour of the majority of Europe's kings and princes; he was particularly valued for his ability to make treaties which, despite apparent concessions, were favourable for Poland.
Poland's development and prosperity, together with its religious tolerance and a liberal mix of influences of Eastern and Western cultures, attracted numerous scholars from many countries. One of the first universities in Central Europe was founded in 1364 in Cracow and it quickly gained international renown. The University, centuries later re-named the Jagiellonian University after its restorer King Jagiełło, provided an education (at first) in three faculties: Lawa, Medicine, and the Liberal Arts (Philosophy).
There are good reasons for the attribute given to Casimir the Great as the one who 'inherited a Poland built of wood, but left it built of stone.' By the time of his death in 1370 the Polish Crown was rich, modern in comparison with its contemporaries, and respected in all of Europe. However, he failed to produce a male heir to succeed him. He was the last monarch of the Piast dynasty, which had ruled in Poland since the early 10th century.
