Why did the Grand Duchy of Lithuania include many ethnic and religious groups?

The Grand Duchy of Lithuania became a multiethnic and multireligious state primarily due to its significant territorial expansion during the 14th century. As the state expanded beyond its original heartland, it incorporated vast East Slavic territories, which brought large populations of Ruthenians (ancestors of modern Belarusians and Ukrainians) into the realm.1

The state’s ability to maintain this diverse empire was rooted in a policy of wide autonomy and religious toleration. Rather than imposing a single culture or faith, the Lithuanian rulers allowed the Ruthenian nobility to retain their Orthodox religion, local authority, and privileges. The administration also adopted Ruthenian models for its legal, financial, and military systems, and used the Ruthenian language for administrative purposes.21

Beyond the Ruthenian majority, the Grand Duchy also included significant minorities of Jews, Tatars, and Germans. This inclusive approach allowed the Lithuanian ruling class to integrate diverse populations effectively, even as the state remained geographically the largest in Europe at the end of the 14th century.12