Ordered down from Salona by Mark Antony, the governor of Illyricum, Publius Vatinius, had occupied Petra camp with one legion. Nothing daunted, Brutus moved his troops into one of the many fortresses dotting the circumvallations built five years ago when Caesar and Pompey the Great had waged siege war there. But Brutus's action proved hardly necessary. Not four days later Vatinius's soldiers opened the gates of Petra camp and went over to Brutus. Their commander Vatinius, they said, had already gone back to Illyricum. Suddenly Brutus owned a force of three legions and two hundred cavalrymen! No one was more surprised than he, no one less sure how to general an army. However, he did understand that fifteen thousand men required the services of a praefectus fabrum to ensure that they were kept fed and equipped, so he wrote to his old friend, the banker Gaius Flavius Hemicillus, who had done this duty for Pompey the Great—would he do the same for Marcus Brutus? That out of the way, the new warlord decided to move south to Apollonia, where sat the official governor of Macedonia, Gaius Antonius.
