In 48 BCE, the Roman general Julius Caesar arrived in Alexandria, where he decided to arbitrate the dispute between Ptolemy and his sister Cleopatra over the throne of Egypt. Siding with Cleopatra, he was besieged by Ptolemy's general Achillas while Ptolemy and Arsinoë were held captive inside the royal palace.
She eventually escaped along with her tutor Ganymedes, executing Achillas and taking over command of his army. Ganymedes proved a gifted tactician, delivering several blows to the Romans. However, Caesar was eventually able to call for reinforcements, and despite driving the Romans out of the harbor, Ganymedes fell into disfavor with the other Egyptian officers. He and Arsinoë were exchanged with Ptolemy, who, against Caesar's terms, continued to rebel against Roman authority until his final defeat at the Battle of the Nile in 47 BCE.