Sosibius

Sosibius (; floruit 221-204 BC) was the chief minister of Ptolemy IV Philopator (221–204 BC), king of Egypt. Nothing is known of his origin or parentage, though he may have been a son of Sosibius of Tarentum; nor is there any account of how he rose to power. He is first attested immediately after the accession of Ptolemy IV in 221 BC, exercising great influence over the 22-year old king alongside Agathocles, the brother of Ptolemy IV's mistress Agathoclea. He remained a major force throughout the reign and helped ensure the smooth succession of Ptolemy V Epiphanes in 204 BC. After that he disappears from the record. Life Accession of Ptolemy IV The historian Polybius characterises him as "the pseudo-guardian of Ptolemy [who] seemed to be a shrewd and long-lasting tool, but was ever doing evil in the kingdom." and says he was responsible for a purge of the royal family which took place shortly after Ptolemy's accession. Ptolemy IV's uncle Lysimachus was probably murdered at this time. His mother Berenice II was believed to support his younger brother Magas, who had held substantial military commands and was popular with the army, so Magas was scalded to death in his bath. Berenice II died shortly afterwards; she is said to have been poisoned. Fourth Syrian War

The Seleucid king Antiochus the Great invaded Coele-Syria in 221 BC. He was rebuffed by the Ptolemaic governor of the region, Theodotus, and forced to turn east as a result of the revolt of his satrap of Media, Molon, but in spring 219 BC he attacked once more, beginning the Fourth Syrian War and quickly captured most of Coele-Syria.

At the beginning of winter, Antiochus III negotiated a ceasefire with Ptolemy IV. Formal peace negotiations followed at Seleucia Pieria, but they do not seem to have been undertaken in good faith on either side. In the midst of this conflict, in July or August 204 BC, Ptolemy IV died in unclear circumstances. A late source, John of Antioch mentions a fire in the palace. Arsinoe III also died at this time. According to Polybius, she was murdered by Sosibius, but another historian, Justin, says that she had been divorced and murdered by Ptolemy IV under the influence of his mistress Agathoclea, shortly before his own death.

An uncertain amount of time elapsed after the death of Ptolemy IV and Arsinoe III (perhaps a week) during which Sosibius and Agathocles kept their deaths secret. The only living member of the royal family was Ptolemy IV's son Ptolemy V Epiphanes, who was about five years old. Some time before September 204 BC, the royal bodyguard and army officers were gathered at the royal palace and Sosibius announced the death of the ruling couple and presented Ptolemy IV's son Ptolemy V Epiphanes to be acclaimed as king, wrapping the diadem around his head. Sosibius read out Ptolemy IV's will, which made Sosibius and Agathocles regents and placed Ptolemy V in the personal care of his mistress Agathoclea and her mother Oenanthe. Polybius thought that this will was a forgery produced by Sosibius and Agathocles themselves and modern scholars tend to agree with him. Sosibius is not heard of again after this event and it is generally assumed that he died, perhaps at the hands of Agathocles. Hölbl suggests that the loss of his acumen was fatal to the regency.