Kingdom of Poland (13th – 15th c.)
Poland was not a solid political entity at the beginning of the 13th century, while its northern frontier was endangered by the pagan Lithuanians and the Prussians. Konrad I, Duke of Masovia (1199-1247) applied to the Teutonic Knights for military assistance. The Teutonic Knights launched several campaigns against the Lithuanians but they started to conquer the Polish lands as well, while southeastern Poland was invaded by the Mongols in 1241. Poland was fragmented but the idea of Polish unity survived and was renewed under Premislas II, Duke of Greater Poland and Gdansk Pomerania who was crowned King of Poland in 1295. He was assassinated one year later and was succeeded by Wenceslaus II Premyslid who was crowned King of Poland in 1300.
Wladyslaw I Lokietek proclaimed himself Premislas’ successor and took advantage of the struggles for the succession in Bohemia after death of Wenceslaus III of Bohemia in 1305. He defeated his opponents and unified Poland in 1305. Wladyslaw I Lokietek was crowned King of Poland in Krakow in 1320 and created a strong central authority. He also rejected the claims of John of Luxembourg to the Polish throne, repulsed the Teutonic Knights in the Battle of Plowce in 1331 and tried to settle the conflicts with Gediminas of Lithuania through friendly politics.
Wladyslaw’s successor Casimir III the Great (1333-1370) continued friendly politics towards Lithuania, conquered Red Russia and Masovia, and made Poland one of the leading European powers after mediating between the kings of Bohemia and Hungary at the Congress of Krakow in 1364. Casimir’s reign was also marked by codification of the Polish civil and criminal law, erection of numerous castles and foundation of the University of Krakow in 1364. Wladyslaw I died without a male descendant in 1370. The Polish throne passed to Louis I of Hungary (1342-1382), the eldest son of Charles Robert and Elisabeth, daughter of Wladyslaw I Lokietek and sister of Casimir the Great. However, the personal union between Poland and Hungary collapsed after the death of Louis I of Hungary.
Louis’ younger daughter Jadwiga assumed the throne of Poland. She married Jogaila, Grand Duke of Lithuania (1377-1434) who was crowned King of Poland as Wladyslaw II Jagiello in 1386. Thus Poland and Lithuania were joined into a personal union known as the Polish-Lithuanian Union which became one of the leading European powers. However, Wladyslaw II Jagiello had to secure his position both in Lithuania and Poland. His right to the Polish throne was challenged after the death of Jadwiga and their few months old daughter in 1399. Wladyslaw legitimized his rule in Poland by marrying Anna of Celje, a granddaughter of Casimir III of Poland and secured his authority in Lithuania with the Union of Vilnius and Radom of 1401. The agreement granted his rival and cousin Vytautas wide autonomy and title Grand Duke. The Polish King would inherit the Grand Duchy if Vytautas died first but in case if Jagiello would die first without an heir the Polish nobility agreed not to elect new king without consulting Vytautas.
Jagiello dealt with the Teutonic Knights after securing his position in Poland and Lithuania. The Polish-Lithuanian forces decisively defeated the Teutonic Knights in the Battle of Grunwald (Tannenberg) in 1410 and dictated the terms of the First Peace of Torun of 1411 which ended the Polish-Lithuanian-Teutonic War (1409-1411). The Poles and Lithuanians demanded only small portions of land but the peace treaty ruined the Teutonic treasury and the Monastic State of the Teutonic Knights never recovered.
Wladyslaw II Jagiello was succeeded by Wladyslaw III (1434-1440) who was Jagiello’s first-born son from his third marriage with Sophia of Halshany. Wladyslaw III had to face opposition of Polish magnates who had their own candidate: Friedrich of Brandenburg who was betrothed to Jadwiga, Jagiello’s daughter by his second wife. However, Wladyslaw’s position was secured when the princess died. He was also elected King of Hungary after the death of Albert II of Habsburg in 1440 but as King of Hungary he had to face the growing threat of the Ottoman Empire. Wladyslaw III organized an anti-Ottoman Crusade but he was killed in the Battle of Varna in 1444. He died without a heir to the throne and was succeeded by his brother Casimir IV Jagiellon (1447-1492), Grand Duke of Lithuania after a three-year interregnum, while the throne of Hungary was meanwhile assumed by Ladislaus the Posthumous.
Casimir’s greatest achievement was victory in the Thirteen Years’ War (1444-1466) against the Teutonic Order which resulted in the incorporation of Prussia into the Kingdom of Poland. Casimir III also created alliances with several European royal houses through his marriage with Elizabeth of Habsburg as well as through marriages of his children. The Jagiellons reigned Bohemia, Hungary, Poland and Lithuania establishing their overlordship over virtually all Eastern and Central Europe by the end of the 15th century.