The Jagiellon Era 1385–1569, was dominated by the union of
Poland with
Lithuania under the
Jagiellon Dynasty, founded by the Lithuanian grand duke
Jogaila. The partnership proved profitable for the Poles and Lithuanians, who played a dominant role in one of the most powerful empires in Europe for the next three centuries.
Poland's partnership with the adjoining Grand Duchy of Lithuania, Europe's last pagan country, provided an immediate remedy to the political and military dilemma caused by the end of the Piast Dynasty. At the end of the fourteenth century, Lithuania was a warlike political unit with dominion over enormous stretches of present-day Belarus and Ukraine. Putting aside their previous hostility, Poland and Lithuania saw that they shared common enemies, most notably the Teutonic Knights; this situation was the direct incentive for the Union of Krewo in 1385. The compact hinged on the marriage of the Polish queen Jadwiga to Jogaila, who became king of Poland under the name Wladyslaw II. In return, the new monarch accepted baptism in the name of his people, obliged to confederate Lithuania with Poland, the intention that proved difficult to fulfil. During the Christianization of Lithuania, the Bishopric of Vilnius was established in 1387 to convert Wladyslaw's subjects to Roman Catholicism. (Eastern Orthodoxy predominated in the bigger part of the Grand Duchy of Lithuania.) From a military standpoint, Poland received protection from the Mongols and Tatars, while Lithuania received aid in its long struggle against the Teutonic Knights.
The alliance of Poland and the Grand Duchy of Lithuania exerted a profound influence on the history of Eastern Europe. Poland and Lithuania would maintain a joint statehood for more than three centuries, forming the "Commonwealth of Two Nations" ranked as one of the leading powers of the continent.
The association produced prompt benefits in 1410 when the forces of Poland and the Grand Duchy of Lithuania defeated the Teutonic Knights at the battle of Grunwald (Tannenberg) during the Polish-Lithuanian-Teutonic War, at last seizing the upper hand in the long struggle with the renegade crusaders. The new Polish and Lithuanian dynasty, called "Jagiellon" after its founder, continued to augment its holdings during the following decades. By the end of the fifteenth century, representatives of the Jagiellons reigned in Bohemia and Hungary as well as Poland and Lithuania, establishing the government of their clan over virtually all of Eastern Europe and Central Europe. This farflung dynastic compound collapsed in 1526 when armies of the Ottoman Empire won a crushing victory at the Battle of Mohács. The death of Louis II of Hungary and Bohemia on the battlefield allowed the Austian Habsburgs to wrest Bohemia and the crown of Hungary from the Jagiellons. The Ottoman conquest of the larger part of Hungary installed the Turks as a menacing presence in the heart of Europe.
