Valentinian III was a Roman Emperor who ruled from 425 to 455 AD. He was born in 419 AD and became emperor at a young age after the death of his predecessor, Honorius. His reign was marked by political instability and the increasing power of military leaders, which weakened the authority of the central government. During his rule, the Western Roman Empire faced numerous challenges, including invasions by various tribes such as the Vandals and Huns. Valentinian III struggled to maintain control and protect the empire's borders, ultimately leading to a decline in Roman power in the West. He was assassinated in 455 AD, which further contributed to the empire's disintegration.