Wladislaw Jagiello, known as Grand Duke Jogaila of Lithuania, was the man responsible for joining Poland and Lithuania against the threat of the Teutonic Knights. Jagiello's ability to analyze political cost and benefits led to maneuvering that would secure Lithuania's safety and individual authority until he produced an heir that would sit on the Polish throne.
Jadwiga was 10 years old when she was crowned “King” of Poland. One year later, in 1386, Grand Duke Jogaila of Lithuania was married to Jadwiga. He took the name Wladislaw and was called “Jagiello” by the Poles. Jadwiga would be the first of 4 wives; she died in 1399 at age 24, leaving Jagiello opportunity to try for sons with future wives.
Jagiello and Poland-Lithuania – Benefits to Both Nations
When Jagiello was elected King of Poland by the Polish nobles, he converted to Catholicism and instructed his boyars in Vilnius to do so as well. This move, along with the protection of Polish forces, would help stave off one of Lithuania's constant irritants, the Teutonic Order.
He knew that the expansive territories captured by his predecessor, Gediminas, needed a strong authoritative figure to rule over them; Lithuanians were a minority within these lands and the non-Lithuanian inhabitants would have little respect for their overlords. As King of Poland, Jagiello's power would increase as would his authority over the lands now belonging to Lithuania.
Poland welcomed Jagiello because the Lithuanian forces could also aid them in protecting the region from Teutonic Knights, but Polish nobles were under the impression that Lithuania would be incorporated into Poland, or at least be subordinate to its neighbor. While Jogaila seemed to promise this in the Treaty of Kreva, he actually had no intention of allowing Poland to absorb Lithuania in such a way.
Jagiello's rivalry with his cousin Vytautas had been problematic until the two resolved to split their powers. Jagiello gave Vytautas the title of Duke of Lithuania, though Jagiello would remain Grand Duke. The two entered a race to produce a male heir who would then become the ruler of both countries – King of Poland and Grand Duke of Lithuania. Jagiello succeeded in the year 1424, and again in 1426, while he was in his 70s. This was the beginning of the Jagiellonian Dynasty of Poland-Lithuania.
References
Bideleux, Robert, and Jeffris, Ian. A History of Eastern Europe: Crisis and Change. London: Routledge, 1989.
Dvornik, Frances. The Slavs in European History and Civilization. New Brunswick: Rutgers University Press, 1962.
Lukowski, Jerzy, and Zawadski, Hubert. A Concise History of Poland. Cambridge: Cambridge University Press, 2006.