cleopatra and her forces were still holding their ground against ptolemy xiii within alexandria when gnaeus pompeius, son of pompey, arrived at alexandria in the summer of 49 bc seeking military aid on behalf of his father. after returning to italy from the wars in gaul and crossing the rubicon in january of 49 bc, caesar forced pompey and his supporters to flee to greece in a roman civil war. in perhaps their last joint decree, both cleopatra and ptolemy xiii agreed to gnaeus pompeius' request. they sent his father 60 ships and 500 troops, including the gabiniani, a move that helped erase some of the debt owed to rome by the ptolemies. the roman writer lucan claims that by early 48 bc pompey named ptolemy xiii as the legitimate sole ruler of egypt; whether true or not cleopatra was forced to flee alexandria and withdraw to the region of thebes. however, by the spring of 48 bc cleopatra traveled to syria with her younger sister arsinoe iv to gather an invasion force that would head to egypt. she returned with an army, perhaps right around the time of caesar's arrival, but her brother's forces, including some gabiniani mobilized to fight against her. they blocked her advance to alexandria, and she had to make camp outside pelousion in the eastern nile delta.