Trakai Island Castle lost its military importance soon after the Battle of Grunwald, when the chief enemy of the Grand Duchy of Lithuania was defeated by the Polish-Lithuanian army. The castle was transformed into a residence and newly decorated from the inside. New frescos were painted on its walls, which have been partially preserved.
The transformation of Trakai Island Castle from a military site to a residence highlights the shift in its purpose following the Battle of Grunwald. The addition of new frescoes adds a decorative element and reflects the changing social context.