 Vytautas, in order to bolster his authority over the Rus' principalities, decided to launch an expedition against Timur, who had subdued the Golden Horde.According to Jan Długosz's chronicle, Jadwiga warned the Polish noblemen not to join Vytautas' campaign because it would end in failure.Halecki says that the great number of Polish knights who joined Vytautas's expedition proves that Długosz's report is not reliable.