Central and eastern Europe in the late Middle Ages was home to many ethnic, cultural, political and social systems. During the fourteenth and fifteenth centuries this region, experienced an increase in settlement density, especially in the kingdom of Poland and certain areas of the grand duchy of Lithuania. The Angevin period lasted sixteen years, maintaining the unity of the kingdom of Poland and its administration. The Angevin regime, in particular during the regency of the nobles from Little Poland, heightened the nobility's sense of its political value. The Lithuanian state, which developed as a monarchy in the thirteenth century, had been consolidated by Grand Duke Gediminas, and was to reach the peak of its political power as an independent state in the second half of the fourteenth century. The Polish-Lithuanian federation now became the great power of central and eastern Europe. Casimir IV's intention was to weave a network of alliances based on the several branches of the Jagiellonian dynasty.