Valentinian II was a Roman Emperor who ruled from 375 to 392 AD. He became emperor at a young age after the death of his father, Valentinian I. His reign was marked by challenges, including conflicts with various tribes and internal power struggles, particularly with his half-brother, Gratian. During his rule, Valentinian II faced significant pressure from the growing influence of Arianism, a Christian sect that opposed the Nicene Creed. He was ultimately a puppet ruler, heavily influenced by his mother, Justina, and the powerful general Theodosius I, who later became the sole emperor of the Roman Empire.