 Before the first series of wars in the 15th century, the Grand Duchy of Lithuania had gained control of a lot of Eastern European territories, from Kiev to Mozhaisk, following the collapse of Kievan Rus' after the Mongol invasions.Over the course of the wars, particularly in the 16th century, the Muscovites were able to expand their domain westwards, taking control of many principalities.The Grand Duchy of Moscow and Lithuania had been involved in a series of conflicts since the reign of Gediminas, who defeated a coalition of Ruthenian princes in the Battle on the Irpin River and seized Kiev, the former capital of Kievan Rus'.