Theodotus of Chios was a trained rhetorician and the tutor of Ptolemy XIII. He was one of the three influential men who led the guardianship for the young Egyptian king after the death of Ptolemy XII (spring of 51 BC). The most powerful of these men was the eunuch and minister Pothinus, the second in rank was the commander-in-chief Achillas and finally in third place was Theodotus. In autumn of 50 BC these three guardians succeeded in securing Ptolemy XIII the participation in the rule of Egypt together with his ambitious older sister Cleopatra VII who in the first year of her accession to the throne (spring of 51 BC) had been able to rule alone. At the end of 49 BC Pothinus and his comrades expelled the Queen from Egypt. So Ptolemy XIII became sole ruler but was still under the influence of his three guardians.
The dethroned Queen soon organized her own army by recruiting mercenaries in Palestine. Ptolemy XIII and his advisers were forced to move with their army into position near the Egyptian border fortress Pelusium, not far from the troops of Cleopatra. At that time (end of July 48 BC) the Roman triumvir Pompey – who had lost the decisive Battle of Pharsalus against Julius Caesar – appeared at the Egyptian coast near Pelusium and asked the allied Pharaoh for asylum and assistance.
The advisers of Ptolemy XIII officially agreed to the petition of Pompey to gain time. After the departure of the Roman messengers a council of state was held to discuss the next steps. Caesar in his Commentarii de Bello Civili and the Roman poet Lucan in his Pharsalia do not mention the participation of Theodotus in this council, but other sources say his suggestion to murder Pompey was accepted. With professional skillfulness Theodotus justified his plan: If Pompey was received, he would become the ruler of Egypt making Caesar the enemy of the country. If Pompey was rejected, he would be discontented with the refusal and Caesar would also be dissatisfied because he had to continue his pursuit; so the best course was to put Pompey to death. Thus Caesar would be satisfied and the murdered Roman general would no longer be a danger because a dead man could not bite. The assassination of Pompey was executed by Lucius Septimius at the behest of Achillas.
Only two days later Caesar arrived with a fleet in Alexandria. According to the Roman historian Livy and the Greek biographer Plutarch it was Theodotus who immediately delivered the signet ring and the head of Pompey to Caesar. But the Roman general was allegedly disgusted and wept. Ancient and modern historians have different opinions if the tears of Caesar were honest. The dictator stayed in Egypt and tried to win influence in the political affairs by claiming to decide the Ptolemaic struggle for the throne. He also demanded the payment of a large sum of money that the Ptolemaic government allegedly owed him for the military restoration of Ptolemy XII in 55 BC. This behaviour caused a war between the Roman dictator and the supporters of Ptolemy XIII. Because Caesar’s army was much too small he could only win the war after long and hard fighting.
Pothinus and Achillas were assassinated in the course of the war but Theodotus managed to escape from Egypt. Some years he eked out a miserable existence. He died in Asia in 43 BC or 42 BC when Marcus Junius Brutus or Gaius Cassius Longinus put him cruelly to death. The famous Roman rhetorician Quintilian tells that a discussion with Caesar about the punishment of Theodotus was a subject in rhetoric schools.