Wikipedia
Olympius (died 652) was an Exarch of Ravenna (649–652). Prior to his term as exarch, Olympius was an imperial chamberlain at Constantinople.
In 649, according to the Liber Pontificalis, the Byzantine Emperor Constans II ordered Olympius to arrest Pope Martin I on the grounds that the pope's election had not been submitted to the emperor for approval. Constans was upset with Martin's condemnation of the Monothelite heresy; he feared that it would resurrect the religious conflict that had plagued the empire. Olympius attempted to gain the support of the citizenry of Rome, as well as the bishops; he also allegedly considered ordering the assassination of Martin. None of his actions, however, met with much success.
Eventually Olympius decided to switch his allegiance and sided with the Pope, simultaneously declaring himself emperor. He marched into Sicily in 652, either to fight the Saracens or the local Byzantine forces. His army was stricken by an unknown disease, which killed Olympius that same year.
Olympius was a minister of the Western Roman Empire, in the court of the emperor Honorius. Olympius orchestrated the fall and execution of the capable general Stilicho, who had effectively been ruling the Western Roman Empire as regent of Honorius for over twelve years.
Germanic tribes invaded Italy in 405. Honorius and the court took refuge in Ravenna, now the capital of the Western Roman Empire. Stilicho defeated the invaders in the mountains of Fæsulæ (Fiesole) near modern day Florence. The Vandals, Alani, and Suevi poured over the Rhine into the interior of Gaul, followed by Franks, Burgundians, and Alemanni, who settled permanently on the left bank of the Rhine. Stilicho entered into negotiations with Alaric, holding out promises of Eastern Illyria to secure his aid. Thereupon the Roman general Constantine, who had crossed over from Britain, appeared in Gaul, and proclaimed himself Emperor. The negotiations with Alaric failed and Alaric demanded an indemnity of 4000 pounds in gold; Stilicho, who had twice saved Italy from barbarian incursion, was suspected by the court of entertaining treasonable plans. The weak-willed Honorius listened to the insinuations of the chancellor Olympius and proceeded to have Stilicho and his family put to immediate execution.
After Stilicho's execution, Olympius prompted Honorius to take a more hostile stance toward the Goths, mostly notably Alaric I, who had previously been cooperating with the Romans. Olympius, through Honorius, orchestrated the massacre of tens of thousands of wives and children of Goths serving in the Roman military. Subsequently, around 30,000 Gothic soldiers defected to Alaric and took part in the first Sack of Rome (410), a key event in the fall of the Western Roman Empire.