vytautas was one of the creators of the union of horodło with poland in 1413. according to the act of the union, the grand duchy of lithuania was to retain a separate grand duke and its own parliament. at the same time both the polish and lithuanian sejms were to discuss all the important matters jointly. this union was important culturally as well as politically because it granted lithuanian christian nobles the same rights as the polish szlachta. this act did not include orthodox nobles. this paved the way for more contacts and cooperation between the nobles of poland and of lithuania.