Following the decisive Battle of Grunwald in 1410 and the Peace of Thorn in 1411, the Polish-Lithuanian alliance emerged as the dominant force in Central and Eastern Europe. However, the complex relationship between Vytautas and Jogaila continued to shape the evolving nature of the Polish-Lithuanian union.
In 1413, the Union of Horodło redefined the relationship between Lithuania and Poland. While Lithuania retained autonomy, the union established the principle that both countries would select future rulers only with mutual consent. The privileges of Catholic Lithuanian nobles were aligned with those of the Polish nobility (szlachta), strengthening the ties between the two states. Additionally, 47 Lithuanian clans were symbolically linked with 47 Polish noble families to foster a future brotherhood and facilitate closer unity. Lithuanian administrative divisions—in Vilnius and Trakai—were created, following Polish governance models, further integrating the two states politically.
The Gollub War with the Teutonic Knights (1419–1422) ended with the Treaty of Melno in 1422, which secured Samogitia as part of Lithuania, marking the end of Lithuanian-Teutonic conflicts. Though Vytautas refrained from pursuing further conquest of East Prussia, the survival of the Teutonic state ensured its presence for centuries. Samogitia, the last pagan region in Europe, was fully Christianized by 1413, completing Lithuania's long journey toward Western Christendom.
In his final years, Vytautas expanded Lithuania’s influence to its greatest extent. After the death of Vasily I of Moscow in 1425, Vytautas and his daughter Sophia of Lithuania—Vasily’s widow—temporarily controlled Moscow and collected tributes from local princes in Pskov and Novgorod. At the Congress of Lutsk in 1429, Vytautas came close to fulfilling his long-standing ambition of being crowned King of Lithuania, with support from Holy Roman Emperor Sigismund. However, political intrigue and his sudden death in 1430 thwarted the plan.
Vytautas’s reign left a lasting legacy. Under his leadership, Lithuania reached the peak of its territorial expansion, securing influence from the Black Sea to the Baltic. His efforts to balance Lithuania’s autonomy with Polish cooperation ensured the stability of the union and shaped the political structure of the region for generations. Though his dream of kingship was never realized, Vytautas's achievements and legend continued to inspire future generations, solidifying his status as one of Lithuania’s greatest rulers.