The 17th century was marked by a continuous series of betrayals, betrayals and defections of the Cossack hetmans and the gentry, along with the troops, to different participants in the conflict. The Cossack colonel Mazepa, who in 1685 was elected hetman, began to acquire increasing importance. He seemed to have succeeded in placing the Cossacks at the service of the new empire. However, it all ended with a monstrous and treacherous betrayal on the eve of the Battle of Poltava. Mazepa made a bet on the victory of the Swedish king. This fatal mistake had dramatic consequences for the entire Dnieper Cossacks.