Complex sentence: After treason by Demian Mnohohrishny and a new Polish offensive Dorosenko concluded an alliance with the Ottomans, who granted him Ukraine, while the hetman agreed to support Ottoman military action with his army.
Split into simpler sentences: After treason by Demian Mnohohrishny and a new Polish offensive Dorosenko concluded an alliance with Ottomans. As a result, Ottoman Empire granted of Ukraine, as well as the hetman agreeing to support Ottoman military action with his army.