Judging that this agreement favored Cleopatra over Ptolemy XIII and that the latter's army of 20,000, including the Gabiniani, could most likely defeat Caesar's army of 4,000 unsupported troops, Potheinos decided to have Achillas lead their forces to Alexandria to attack both Caesar and Cleopatra. After Caesar managed to execute Potheinos, Arsinoe IV joined forces with Achillas and was declared queen, but soon afterward had her tutor Ganymedes kill Achillas and take his position as commander of her army. Ganymedes then tricked Caesar into requesting the presence of the erstwhile captive Ptolemy XIII as a negotiator, only to have him join the army of Arsinoe IV. The resulting siege of the palace, with Caesar and Cleopatra trapped together inside, lasted into the following year of 47 BC.