How old was Alexander the Great when he went on his first campaign?

He was then 20 years old. So in 978 a war broke out between him and his brother Yaropolk. The general battle between the brothers took place near Kiev. There Yaropolk’s army was defeated. In this connection, Prince Vladimir was able to seize power in Kiev. In general, his reign spans 980-1015. During this period of time, Russia expanded its power even more, and most importantly turned into a Christian state.