- In May 392, Valentinian II, sole emperor in the west, who was dominated by his general Arbogastes, was either killed by him or persuaded to commit suicide.
- Arbogastes, being a Frank, was unable to rule himself, so he had Eugenius appointed emperor in the west.
- Eugenius was originally a teacher of rhetoric and grammar, and was effectively the puppet of Arbogastes.
- Theodosius, emperor in the east, was married to the sister of Valentinian, and she pleaded with him to avenge her brother.
- Theodosius arrived at the Julian Alps with an army to attack Eugenius and Arbogastes. Finding the passes heavily fortified, he managed to turn the loyalty of Eugenius's troops and defeat him at the Battle of the River Frigidus, 394.
- Eugenius was put to death on September 6th, 394, and a few days later Arbogastes, who had fled into the mountains, committed suicide.