Poland during the Jagiellon dynasty

The rule of the Jagiellonian dynasty in Poland between 1386 and 1572 spans the late Middle Ages and early Modern Era in European history. The dynasty was founded by the Lithuanian Grand Duke Jogaila (Władysław II Jagiełło), whose marriage to Queen Jadwiga of Poland formed a Polish–Lithuanian union. The partnership brought vast territories controlled by the Grand Duchy of Lithuania into Poland's sphere of influence and proved beneficial for both the Polish and Lithuanian people, 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 maintained an ongoing conflict with the Teutonic Knights. The struggles led to a major battle, the Battle of Grunwald of 1410, but there was also the milestone Peace of Thorn of 1466 under King Casimir IV Jagiellon; the treaty created the future Duchy of Prussia. In the south, Poland confronted the Ottoman Empire and the Crimean Tatars, and in the east helped Lithuania fight the Grand Duchy of Moscow. Poland's and Lithuania's territorial expansion included the far north region of Livonia.

In the Jagiellonian period, Poland developed as a feudal state with a predominantly agricultural economy and an increasingly dominant landed nobility. The Nihil novi act adopted by the Polish Sejm in 1505 transferred most of the legislative power in the state from the monarch to the Sejm. This event marked the beginning of the period known as "Golden Liberty", when the state was ruled by the "free and equal" members of the Polish nobility.

...
Wikipedia