In 327 bc, Quintus Publilius Philo, one of Rome's two consuls for that year, was commander of an army besieging the city of Neapolis (modern Naples), which had sided with the neighboring Samnites in their long struggle with Rome for dominance in central Italy. By immemorial custom, consuls – the chief executive officers of the Roman Republic – held office for a single year and were not normally eligible for (immediate) reelection. When the elections of magistrates for the coming year were held, however, it was deemed advisable not to replace the senior commander in the middle of these ongoing operations. Instead, the popular assembly passed a motion that “Quintus Publilius Philo should on the expiration of his consulship conduct the campaign in place of a consul [pro consule] until the war with the Greeks was concluded,” according to the preeminent historian of the Republic. Thus did the Romans create their first “proconsul.”

Before exploring further the nature of proconsular decision-making in classical Rome and its historical evolution there, some basic points need to be made. To the extent that the notion of proconsulship or proconsular rule remains of interest today, it is in the context of discussions of (a putative) American “empire” and the role of regional American military commanders within it. In the Roman context, however, proconsulship in the proper and interesting sense of the term is a product of the Roman Republic, not the Roman Empire. The Roman Empire (27 bc–476 ad) indeed inherited institutional forms and terminology from the Republic that preceded it, proconsulship included; but imperial proconsuls were something quite different from their republican counterparts. As we shall see, the reorganization of the Roman government effected by the first emperor, Caesar Augustus, set out to solve the fundamental problem that proconsular authority had come to pose for the Republic. It did so by reducing “proconsul” to an essentially honorific title with largely administrative duties and – the critical point – no command of military forces.