Short answers, pulled from the story.
The Grand Duchy of Lithuania emerged in the thirteenth century and was dissolved in 1795, when its remaining territory was fully partitioned among the Russian Empire, the Kingdom of Prussia, and Austria following the Kościuszko Uprising. The state existed for roughly five centuries.
Mindaugas was the first ruler of the Grand Duchy of Lithuania. He was crowned King of Lithuania on the 6th of July 1253, following a papal bull from Pope Innocent IV that formally recognized the Kingdom of Lithuania. He was later assassinated in 1263 alongside his two sons, Ruklys and Rupeikis.
By 1440 the Grand Duchy of Lithuania had become the largest state in Europe, stretching from the Baltic Sea in the north to the Black Sea in the south. At its greatest territorial extent the duchy covered between 800,000 and 930,000 square kilometers.
The Battle of Grunwald in 1410, commanded on the Lithuanian side by Vytautas the Great, ended in a decisive Polish-Lithuanian victory over the Teutonic Order. It concluded a war between Lithuania and the military orders that had lasted more than two hundred years, one of the longest wars in European history.
The Grand Duchy used Chancery Ruthenian for internal administration, Latin for correspondence with western powers, and German for dealings with the Teutonic Order. Polish gradually replaced Ruthenian from the sixteenth century onward and was confirmed as the sole administrative language in 1697. The first official document written in Lithuanian was a translation of the Constitution of May 3, issued in 1791.
The Union of Lublin in 1569 formally merged the Grand Duchy of Lithuania with the Kingdom of Poland to create the Polish-Lithuanian Commonwealth. Military pressure from Moscow and the loss of territory under the 1522 peace treaty following the Battle of Orsha drove Lithuania to accept closer union with Poland. The Grand Duchy retained separate laws, army, treasury, and courts within the new federation.