Jogaila (Lithuanian: [jɔˈɡâːɪɫɐ] ; c. 1352/1362 – 1 June 1434), later Władysław II Jagiełło (Polish: [vwaˈdɨswaf jaˈɡʲɛwwɔ] ), was Grand Duke of Lithuania beginning in 1377 and King of Poland from 1386 until his death. As Grand Duke, he ruled Lithuania from 1377 to 1381 and from 1382 to 1401, at which time he became the Supreme Duke of Lithuania in exchange for naming his cousin Vytautas as the new Grand Duke. Władysław II initially served as King of Poland alongside his wife Jadwiga until her death in 1399, and then the sole ruler until his own death in 1434.
Raised a Lithuanian polytheist, he converted to Catholicism in 1386 and baptized as Ladislaus (Polish: Władysław) in Kraków, married the young Queen Jadwiga, and was crowned King of Poland as Władysław II Jagiełło. In 1387, he converted Lithuania to Catholicism. His sole reign in Poland started in 1399, upon the death of Queen Jadwiga, lasted a further thirty-five years, and laid the foundation for the centuries-long Polish–Lithuanian union. He was a member of the Jagiellonian dynasty in Poland that bears his name and was previously also known as the Gediminid dynasty in the Grand Duchy of Lithuania. The dynasty ruled both states until 1572, and became one of the most influential dynasties in late medieval and early modern Europe.
Jogaila was the last pagan ruler of medieval Lithuania. After he became King of Poland, as a result of the Union of Krewo, the newly formed Polish-Lithuanian union confronted the growing power of the Teutonic Order. The allied victory at the Battle of Grunwald in 1410, followed by the Peace of Thorn, secured the Polish and Lithuanian borders and marked the emergence of the Polish–Lithuanian alliance as a significant force in Europe. The reign of Władysław II Jagiełło extended Polish frontiers and is often considered the beginning of Poland's Golden Age.
Little is known of Jogaila's early life, and even his year of birth is uncertain. Previously, historians assumed he was born around 1352, but some recent research suggests a later date — about 1362. He was the son of Algirdas, Grand Duke of Lithuania of the Gediminid dynasty, and his second wife, Uliana of Tver, who was the daughter of the Yaroslavichi prince Aleksandr of Tver. Joagaila's name had a meaning of more courageous and superior than others. The young Prince spent most of his early time in Vilnius, at his father's manor.
Jogaila was designated by his father to be his heir (replacing his older half-brother Fiodor in that role) and ascended the Lithuanian throne after Algirdas's death in 1377. Depending on which year he was born with, he was either around 14 or 24 years old at the time of becoming the Grand Duke. The former possibility is supported by the fact during Jogaila's early reign his mother Uliana of Tver acted as regent; additionally, Vytautas the Great in his Memorial noted that his father Kęstutis (Algirdas's brother) ruled over Lithuania "until he [Jogaila] grew up and people get used to him", which suggests Jogaila would have been very young and presumably underaged – therefore in his teens rather than 20s – when he had come to the throne.
The Grand Duchy of Lithuania, over which Jogaila ruled, was a political entity composed of two leading, but very different nationalities and two political systems: ethnic Lithuania in the northwest and the vast Ruthenian territories of former Kievan Rus', comprising the lands of modern Ukraine, Belarus, and parts of western Russia. At first, the young Grand Duke — like his father — based his rule in the southern and eastern territories of Lithuania, while his uncle, Kęstutis, the Duke of Trakai, continued to rule the north-western region. Jagiełło's succession, however, soon placed this system of dual rule under strain.
At the start of his reign, Jogaila was preoccupied with unrest in the Lithuanian Rus' lands. In 1377–1378, Andrei of Polotsk, the eldest son of Algirdas, challenged Władysław II Jagiełło's authority and sought to become Grand Duke. In 1380, Andrei and another brother, Demetrius I Starshy, sided with Prince Dmitri Donskoi against Jogaila's alliance with emir Mamai, de facto khan of the Golden Horde. Jagiełło failed to support Mamai, lingering in the vicinity of the battlefield, which led to Mamai's army's significant defeat at the hands of Prince Dmitri in the Battle of Kulikovo. The Muscovites' Pyrrhic victory over the Golden Horde, in the long term, signified, however, the beginning of a slow climb to power by the Grand Duchy of Moscow, which became within a century the most serious rival and threat to the integrity, well-being and survival of Lithuania. However, in 1380, Muscovy was greatly weakened by tremendous losses suffered during the battle and thus, in the same year, Jagiełło was free to begin a struggle for supremacy with Kęstutis.
In the northwest, Lithuania faced constant armed incursions from the Teutonic Knights — founded after 1226 to fight and convert the pagan Baltic tribes of Prussians, Yotvingians and Lithuanians. In 1380, Jagiełło concluded the secret Treaty of Dovydiškės, directed against Kęstutis. When Kęstutis discovered the plan, the Lithuanian Civil War began. He seized Vilnius, overthrew Jogaila, and pronounced himself the Grand Duke in his place. In 1382, Jogaila raised an army from his father's vassals and confronted Kęstutis near Trakai. Kęstutis and his son Vytautas entered Jagiełło's encampment for negotiations but were tricked and imprisoned in the Kreva Castle, where Kęstutis was found dead, probably murdered, a week later. Vytautas escaped to the Teutonic fortress of Marienburg and was baptised there under the name Wigand.
Jogaila formulated the Treaty of Dubysa, which rewarded the Knights for their aid in defeating Kęstutis and Vytautas by promising Christianisation and granting them Samogitia west of the Dubysa river. However, when Jagiełło failed to ratify the treaty, the Knights invaded Lithuania in the summer of 1383. In 1384, Jogaila reconciled with Vytautas, promising to return his patrimony in Trakai. Vytautas then turned against the Knights, attacking and looting several Prussian castles.
It is known that Jagiełło, being ethnic Lithuanian in the male line, himself knew and spoke in the Lithuanian language with Vytautas, his cousin from the Gediminids dynasty. Also, during the Christianisation of Samogitia, none of the clergy, who came to Samogitia with Jogaila, were able to communicate with the natives, therefore the Grand Duke himself taught the Samogitians about the Catholicism, thus he was able to communicate in the Samogitian dialect of the Lithuanian language. According to the Teutonic Order's testimonial, he could not read nor write, and had to listen to others reading for him.
Jogaila's Russian mother Uliana of Tver urged him to marry Sofia, daughter of Prince Dmitri of Moscow, who required him first to convert to Orthodoxy. That option, however, was unlikely to halt the crusades against Lithuania by the Teutonic Knights, who regarded Orthodox Christians as schismatics and little better than heathens. Władysław II Jagiełło chose therefore to accept a Polish proposal to become a Catholic and marry then-eleven-year-old Queen Jadwiga of Poland. The nobles of Lesser Poland made this offer to Władysław II Jagiełło for many reasons. They wanted to neutralise the dangers posed by Lithuania itself and to secure the fertile territories of Galicia–Volhynia. The Polish nobles saw the offer as an opportunity for increasing their privileges and avoiding Austrian influence, brought by Jadwiga's previous fiancé William, Duke of Austria.
On 14 August 1385 in Kreva Castle, Jagiełło confirmed his prenuptial promises in the Union of Krewo (Union of Kreva). The promises included the adoption of Christianity, repatriation of lands "stolen" from Poland by its neighbours, and terras suas Lithuaniae et Russiae Coronae Regni Poloniae perpetuo applicare, a clause interpreted by historians to mean anything from a personal union between Lithuania and Poland to a complete incorporation of Lithuania into Poland. The agreement at Kreva has been described both as far-sighted and as a desperate gamble.