The Grand Duchy expanded to include large portions of the former
Kievan Rus' and other neighbouring states, including what is now
Belarus and parts of
Ukraine,
Latvia,
Poland and
Russia. At its greatest extent, in the 15th century, it was the largest state in Europe.[6] It was a multi-ethnic and multi-confessional state, with great diversity in languages, religion, and cultural heritage.
The consolidation of the Lithuanian lands began in the late 12th century.
Mindaugas, the first ruler of the Grand Duchy, was crowned as
Catholic King of Lithuania in 1253. The pagan state was targeted in the
religious crusade by the
Teutonic Knights and the
Livonian Order. The rapid territorial expansion started at the late reign of
Gediminas[7] and continued to expand under the diarchy and co-leadership of his sons
Algirdas and
Kęstutis.[8] Algirdas's son
Jogaila signed the
Union of Krewo in 1386, bringing two major changes in the history of the Grand Duchy of Lithuania:
conversion to Christianity and establishment of a
dynastic union between the Grand Duchy of Lithuania and the
Crown of the Kingdom of Poland.[9]