III. Valentinianus was born in 419. III. The full name of Valentinianus is Flavius Placidius Valentinianus. Valentinian was the emperor of the Roman state in 423.
Valentinianus was an emperor when he was 4 years old. That is why the Roman state was governed by Valentinian's mother. But as the age of Valentinian progressed, Valentinian began to rule the Roman state.
Valentinianus has raised tax rates. This led to many rebellions in the Roman state. Valentinianus has not finished the rebellion that started in Britain. And that's why the Roman Empire had to leave Britain.
It also started rebellion in Spain. And the Roman state has lost it in Spain. At the same time, Atilla, the king of Hun, started a war against Valentinian. And Atilla almost looted the whole of Italy.
Valentinian tried to fight against these events and it always failed. Valentinianus was murdered in 455.