He chose Choosing to continue his invasion Attack now because he expected Swedish reinforcements and the alliance of the Cossacks under Ivan Mazepa .

The reinforcing Cause_change_of_strength Swedish army , however , was ambushed Attack by Russians , and a Russian army under Aleksandr Danilovich Menshikov had destroyed Destroying Mazepa 's capital and chased Self_motion him to Charles with just thirteen hundred men .