key dates in minamotos life 

His first victory-

The Genpei War was in 1180–1185. It was a conflict between the Taira and Minamoto clans during the late-Heian period of Japan. It ended up in the fall of the Taira clan and the establishment of the Kamakura shogunate under Minamoto Yoritomo in 1192.

The name "Genpei"  comes from readings of the kanji "Minamoto" and "Taira". The conflict is also known in Japanese as the Jishō-Juei War . After the two eras between which it took place.

It began with Minamoto support for a different nominee to take the throne, in conflict with the Taira's nomination. The ensuing Battle of Uji took place just outside Kyoto, starting a five-year long war, concluding with a decisive Minamoto victory in the naval Battle of Dan-no-ura.

becoming the first shogun

This was a very big deal for becoming a shogun and especially at such a young age.

 Minamoto Yoritomo is one of the major figures in Japanese history. He established the first of the three shogunates (bakufu), that is, military governments, in Japanese history.