The Lithuanian Civil War of 1389–92 was the second civil conflict between Jogaila, King of Poland and Grand Duke of Lithuania, and his cousin Vytautas.
 At issue was control of the Grand Duchy of Lithuania, then the largest state in Europe.
 Jogaila had been crowned King of Poland in 1386; he installed his brother Skirgaila as ruler of Lithuania.
 Skirgaila proved unpopular and Vytautas attempted to depose him.
 When his first attempt to take the capital city of Vilnius failed, Vytautas forged an alliance with the Teutonic Knights, their common enemy – just as both cousins had done during the Lithuanian Civil War between 1381 and 1384.
 Vytautas and the Knights unsuccessfully besieged Vilnius in 1390.
 Over the next two years it became clear that neither side could achieve a quick victory, and Jogaila proposed a compromise: Vytautas would become Grand Duke and Jogaila would remain Superior Duke.
 This proposal was formalized in the Ostrów Agreement of 1392, and Vytautas turned against the Knights.
 He went on to reign as Grand Duke of Lithuania for 38 years, and the cousins remained at peace.
Soviet–Lithuanian Non-Aggression Pact (Lithuanian: "Lietuvos–TSRS nepuolimo sutartis") was a non-aggression pact, signed between the Soviet Union and Lithuania on September 28, 1926.
 The pact confirmed all basic provisions of the Soviet–Lithuanian Peace Treaty of 1920.
 The Soviet Union continued to recognize Vilnius and Vilnius Region to Lithuania, despite the fact that the territories were under Polish control since the Żeligowski's Mutiny in 1920.
 It also recognized Lithuania's interests in the Klaipėda Region.
 In exchange Lithuania agreed not to join any alliances directed against the Soviet Union, which meant international isolation at the time when Soviet Union was not a member of the League of Nations.
 Ratifications were exchanged in Kaunas on November 9, 1926, and the pact became effective on the same day.
 The pact was registered in "League of Nations Treaty Series" on March 4, 1927.
Jogaila, later Władysław II Jagiełło (] ) (c. 1352/1362 – 1 June 1434) was the Grand Duke of Lithuania (1377–1434) and then the King of Poland (1386–1434), first alongside his wife Jadwiga until 1399, and then sole King of Poland.
 He ruled in Lithuania from 1377.
 Born a pagan, in 1386 he converted to Catholicism and was baptized as Władysław in Kraków, married the young Queen Jadwiga, and was crowned King of Poland as Władysław II Jagiełło.
 In 1387 he converted Lithuania to Christianity.
 His own reign in Poland started in 1399, upon the death of Queen Jadwiga, and 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 Central and Eastern Europe.
 During his reign, the Polish-Lithuanian state was the largest state in the Christian world.
The Pact of Vilnius and Radom (Polish: "Unia wileńsko-radomska" , Lithuanian: "Vilniaus-Radomo sutartis" ) was a set of three acts passed in Vilnius, Grand Duchy of Lithuania, and confirmed by the Crown Council in Radom, Kingdom of Poland in 1401.
 The union amended the earlier act of the Union of Krewo (1385) and confirmed the Ostrów Agreement (1392).
 Vytautas, Grand Duke of Lithuania, became fully in charge of the Lithuanian affairs, while Władysław II Jagiełło, King of Poland, reserved the rights of an overlord.
 After the death of Vytautas, Lithuania was to be ruled by Władysław II Jagiełło or his legal heir.
 The union is generally seen as strengthening of the Polish–Lithuanian union.
The Lithuanian Civil War of 1381–1384 was the first struggle for power between the cousins Jogaila, Grand Duke of Lithuania and later King of Poland, and Vytautas the Great.
 It began after Jogaila signed the Treaty of Dovydiškės with the Teutonic Knights which was aimed against his uncle Kęstutis, father of Vytautas.
 Kęstutis briefly seized power in the Grand Duchy, but was betrayed by adherents of Jogaila primarily from Vilnius.
 During negotiations for a truce Kęstutis and Vytautas were arrested and transported to the Kreva Castle.
 Kęstutis died there a week later but Vytautas managed to escape and then sought an alliance with the Teutonic Knights.
 Subsequently their joint forces raided Lithuanian lands.
 Eventually the cousins were reconciled as Jogaila needed internal stability in anticipation of negotiations with the Grand Duchy of Moscow and the Kingdom of Poland regarding the possible Christianization of Lithuania.
 The war did not settle the power struggle; it continued during the next Lithuanian Civil War (1389–1392) which was resolved by the signing of the Ostrów Agreement.
 After more than ten years of struggle, Vytautas finally became the Grand Duke of Lithuania and ruled the country for thirty-eight years.
The Union of Horodło or Pact of Horodło was a set of three acts signed in the town of Horodło on 2 October 1413.
 The first act was signed by Władysław II Jagiełło, King of Poland, and Vytautas, Grand Duke of Lithuania.
 The second and third acts were composed by the Polish nobility (szlachta) and Lithuanian boyars respectively.
 The union amended the earlier Polish–Lithuanian unions of Krewo and Vilnius–Radom.
 Politically, Lithuania received more autonomy as, after the death of Vytautas, the Lithuanian nobles could choose another Grand Duke instead of passing the title to Władysław II Jagiełło or his heir.
 However, culturally, Lithuania and Poland grew closer.
 Lithuania adopted Polish institutions of castellans and voivodes. Catholic Lithuanian nobles and church officials were granted equal rights with the Polish nobles and clergy.
 Forty-seven selected Lithuanian nobles were adopted by Polish families and granted Polish coats of arm.
 Thus the union signified the beginnings of Polonization of Lithuanian culture and the rise of the Lithuanian nobility.
 It was one of the major steps towards the modernization and Europeanization of Lithuania.
Radom ( ; Yiddish: ראָדעם‎ "Rodem") is a city in east-central Poland with 219,703 inhabitants (2013).
 It is located 100 km south of Poland's capital, Warsaw, on the Mleczna River, in (as of 1999) the Masovian Voivodeship, having previously been the capital of Radom Voivodeship (1975–1998).
 Despite being part of the Masovian Voivodeship, the city historically belongs to Lesser Poland.
 For centuries, Radom was part of the Sandomierz Voivodeship of the Kingdom of Poland and the later Polish-Lithuanian Commonwealth.
 It was an important center of administration, having served as seat of the Crown Council.
 The Pact of Vilnius and Radom was signed there in 1401, and the Nihil novi and Łaski's Statute were adopted by the Sejm at Radom's Royal Castle in 1505.
 In 1976, it was a center of anti Communist street protests.
The Ostrów or Astrava Agreement (Lithuanian: "Astravos sutartis" , Belarusian: Востраўскае пагадненне , Polish: "Ugoda w Ostrowie" ) was a treaty between Jogaila (Władysław II Jagiełło), King of Poland and Grand Duke of Lithuania, and his cousin Vytautas the Great, signed on 4 August 1392.
 The treaty ended the destructive Lithuanian Civil War, launched in 1389 by Vytautas who hoped to gain political power, and concluded the power struggle between the two cousins that erupted in 1380 after Jogaila secretly signed the Treaty of Dovydiškės with the Teutonic Knights.
 The Ostrów Agreement did not stop attacks from the Teutonic Knights and the territorial dispute over Samogitia continued up to 1422.
 According to the treaty, Vytautas became the ruler of Lithuania (styled Grand Duke), but he also acknowledged Jogaila's (styled Supreme Duke) rights to Lithuania.
 The details of the Polish–Lithuanian relationship were clarified in several later treaties, including the Union of Vilnius and Radom in 1401 and Union of Horodło in 1413.
The Union of Grodno was a series of acts of the Polish–Lithuanian union between Kingdom of Poland and Grand Duchy of Lithuania.
 The first acts were signed in 1432 during the Lithuanian Civil War of 1431–1435.
 The acts confirmed the Union of Vilnius and Radom (1401).
 The Union established Sigismund Kęstutaitis as the Grand Duke of Lithuania and re-established Władysław II Jagiełło's seniority and dynastic interest in Lithuania.
Andrei of Polotsk (Belarusian: Андрэй Альгердавіч , Lithuanian: "Andrius Algirdaitis" Polish: "Andrzej Olgierdowic" , ca. 1325 – 12 August 1399, in the Battle of the Vorskla River) was the eldest son of Algirdas, Grand Duke of Lithuania, and his first wife Maria of Vitebsk.
 He was Duke of Pskov (through his deputy Yuri, 1342–1348) and Polotsk (1342–1387).
 As the eldest son of the Grand Duke, Andrei claimed his right to the throne after his father's death in 1377.
 Algirdas left Jogaila, his eldest son with his second wife Uliana of Tver, as the rightful heir.
 Andrei's rivalry with Jogaila, Grand Duke of Lithuania and later King of Poland, eventually led to his demise.

Question: What is the name of the Grand Duke of Lithuania, then the King of Poland, who reserved the rights of the overlord under the Pact of Vilnius and Radom?
Answer: Władysław II Jagiełło