How did Gediminas expand the Grand Duchy of Lithuania?

Gediminas expanded the Grand Duchy of Lithuania by establishing a vast domain that encompassed Lithuania proper, Samogitia, Volhynia, northwestern Ukraine, and Belorussia as far as the Dnieper River.1

To secure and grow his realm, he employed a multifaceted strategy:

• Diplomatic Alliances: He strengthened his position by forming an alliance with Poland in 1325, solidified by the marriage of his daughter Aldona to Casimir, the son of King Władysław I the Short.1
• Economic Development: He invited monks, merchants, and artisans from the Hanseatic League to settle in Lithuania by offering them protection and privileges, which helped modernize and integrate his territories.1
• Strategic Diplomacy: He engaged in direct negotiations with the Holy See to seek protection against the Teutonic Order, framing his resistance as a matter of national defense rather than religious hostility.1
• Capital Development: He established Vilnius as his capital, creating a centralized hub for his administration and diplomatic efforts.1