In 1618, Sahaidachny joined the Anti-Turkish Holy League. While he was battling the Turks, the Polish–Lithuanian Commonwealth requested his assistance for war with Muscovy (Russian Tsardom); they wanted him to provide Władysław IV Vasa, the King of the Polish–Lithuanian Commonwealth, with 20,000 Cossacks near Moscow. Sahaidachny did, and seized the forts in the cities of Putivl, Kursk, Livny, Yelets and many others. Near Serpukhov Sahaidachny forced the Muscovite army to flee. The Muscovite troops under command of the voivode G. Volkonsky forced Cossacks to take a detour, but were unable to stop the advance of the Cossacks regiments to Moscow. In September 1618 he forced to flee the army of another Muscovite nobleman Vasilii Buturlin. Later, united army of Jan Karol Chodkiewicz and Sahaidachny sieged Moscow and 11 October unsuccessful attempted to take the Arbat Gates.