Honorius (who would move the western capital from Milan to Ravenna in 402, in the wake of Alaric*'s march), along with his older brother, Arcadius (377/378-408), would rule the Roman Empire after his father Theodosius I died, in 395. Stilicho, adviser to Theodosius I, claimed that before dying the emperor had named him regent of Honorius and protector of Arcadius. Honorius had been junior emperor for two years when his father died. Arcadius had been nominal emperor in the east for a decade and had his own advisors.
Between 394 and 408, Stilicho served Honorius as master of soldiers as well as regent. The emperor married, in turn, both of Stilicho's daughters, Maria and Aemilia Materna Thermania. But Stilicho had enemies within the empire who used his ungainly barbaric ties, his seemingly ambitious drive into the eastern Empire, his alliance with Alaric, and the usurpation of Constantine III, to convince Honorius to execute him. So on August 22, 408, Honorius had Stilicho, his regent and father-in-law, beheaded.
This was one of Honorius' many disastrous political moves. Stilicho was a positive link to and formidable shield against Alaric the Goth. With Stilicho dead, Alaric was in a better position to make demands of and lay siege against Rome, which he did when the emperor failed to pay for services. This ultimately led to Alaric's sacking of Rome in 410. Two years later, Honorius' half-sister, Placidia, was forced to marry the barbarian Athaulf who led the Visigoths to Gaul. Chaos followed, partly due to the previous crossing of the Rhine by the Vandals and others who occupied Spain and partly due to Constantine III's usurpation, which led to the loss of Roman control over Britain.
Honorius suffered a dwindling rule before dying childless on August 25, 423 of natural causes while at Ravenna.
Alaric was king of the Visigoths who ruled from 395-410/11. He had served under Theodosius in 394 at the Battle of the Frigidus, and sacked Rome in 410.