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HomeUncategorizedHow to Roman Republic 101, Part IIIb: Imperium

How to Roman Republic 101, Part IIIb: Imperium

This is the second section of the third part of our planned five part series (I, II, IIIa) on the structure of the Roman Republic during the third and second centuries, the ‘Middle’ Republic. Last week we discussed the overall structure of the ‘career path’ for a Roman politician and the first few offices along that path. This week we’re going to look at the upper-steps of that career path, the offices of praetor and consul and the particular set of powers they possess, called imperium, along with the pro-magistrate forms of these positions. Now I should note at the outset that we have skipped one office on our way through, the tribunes of the plebs; we’ll get to that office next week to discuss its oddities and unusual powers.

The praestorship and the consulship are the highest Roman offices (the censorship being more of a ‘victory lap’) and the two offices that wield direct military and judicial authority. These are also the offices where competition in the cursus honorum starts to get fierce, as the eight quaestors must compete for just six praetorships and those six praetors can expect to compete for just two – always two – consulships. It is worth keeping in mind as we go through this that on the one hand these offices are largely confined to a small Roman elite, the nobiles, composed of families (both patrician and plebeian) that have been successful in politics over generations, but at the same time it is the popular assemblies which choose ‘winners’ and ‘losers’ from among the nobiles by deciding who gets to proceed to the next round of the political elimination context, and who is forever going to sit in the Senate as a former quaestor and nothing more.

Now I am the only one of this blog who gets to have imperium (apparently ACOUP operates in the imperial where I have imperium and the guest-posters are my legati), but Patrons at the patres et matres conscripti level can still advise me on how to use my imperium! You don’t even have to have held the quaestorship! As always, if you like this, please share it! If you want updates whenever a new post appears, you can click below for email updates or follow me on twitter (@BretDevereaux) for updates as to new posts as well as my occasional ancient history, foreign policy or military history musings, assuming there is still a Twitter by the time this post goes live. I am also on Bluesky ( and (less frequently) Mastodon (


What connects these offices in particular is that they confer imperium, a distinctive concept in Roman law and governance. The word imperium derives from the verb impero, ‘to command, order’ and so in a sense imperium simply means ‘command,’ but in its implication it is broader. Imperium was understood to be the power of the king (Cic. Leg. 3.8), encompassing both the judicial role of the king in resolving disputes and the military role of the king in leading the army. In this sense, imperium is the power to deploy violence on behalf of the community: both internal (judicial) violence and external (military) violence.

That power was represented visually around the person of magistrates with imperium through the lictors (Latin: lictores), attendants who follows magistrates with imperium, mostly to add dignity to the office but who also could act as the magistrates ‘muscle’ if necessary. The lictors carried the fasces, a set of sticks bundled together in a rod; often in modern depictions the bundle is thick and short but in ancient artwork it is long and thin, the ancient equivalent of a police-man’s less-lethal billy club. That, notionally non-lethal but still violent, configuration represented the imperium-bearing magistrate’s civil power within the pomerium (recall, this is the sacred boundary of the city). When passing beyond the pomerium, an axe was inserted into the bundle, turning the the non-lethal crowd-control device into a lethal weapon, reflective of the greater power of the imperium-bearing magistrate to act with unilateral military violence outside of Rome (though to be clear the consul couldn’t just murder you because you were on your farm; this is symbolism). The consuls were each assigned 12 lictors, while praetors got 6. Pro-magistrates had one fewer lictor than their magistrate versions to reflect that, while they wielded imperium, it was of an inferior sort to the actual magistrate of the year.

From the British Museum (inv. 1983,1229.1) a bronze figurine dating to the late first century showing a lictor bearing the fasces as they would be carried outside of the pomerium, with the axe inserted.

What is notable about the Roman concept of imperium is that it is a single, unitary thing: multiple magistrates can have imperium, you can have greater or lesser forms of imperium, but you cannot break apart the component elements of imperium. This is a real difference from the polis, where the standard structure was to take the three components of royal power (religious, judicial and military) and split them up between different magistrates or boards in order to avoid any one figure being too powerful. For the Romans, the royal authority over judicial and military matters were unavoidably linked because they were the same thing, imperium, and so could not be separated. That in turn leads to Polybius’ awe at the power wielded by Roman magistrates, particularly the consuls (Polyb. 6.12); a polis wouldn’t generally focus so much power into a single set of hands constitutionally (keeping in mind that tyrants are extra-constitutional figures).

So what does imperium empower a magistrate to do? All magistrates have potestas, the power to act on behalf of the community within their sphere of influence. Imperium is the subset of magisterial potestas which covers the provision of violence for the community and it comes in two forms: the power to raise and lead armies and the power to organize and oversee courts. Now we normally think of these powers as cut by that domi et militiae (“at home and on military service”) distinction we discussed earlier in the series: at home imperium is the power to organize courts (which are generally jury courts, though for some matters magistrates might make a summary judgement) and abroad the power to organize armies. But as we’ll see when we get to the role of magistrates and pro-magistrates in the provinces, the power of legal judgement conferred by imperium is, if anything, more intense outside of Rome. That said it is absolutely the case that imperium is restrained within the pomerium and far less restrained outside of it.

From the British Museum (inv. G.2680) a gold stater (minted in 42 BC) showing on the obverse Brutus as consul with two lictors accompanying him.

There were limits on the ability of a magistrate with imperium to deploy violence within the pomerium against citizens. The Lex Valeria, dating to the very beginning of the res publica stipulated that in the case of certain punishments (death or flogging), the victim had the right of provocatio to call upon the judgement of the Roman people, through either an assembly or a jury trial. That limit to the consul’s ability to use violence was reinforced by the leges Porciae (passed in the 190s and 180s), which protected civilian citizens from summary violence from magistrates, even when outside of Rome. That said, on campaign – that is, militae rather than domi – these laws did not exempt citizen soldiers from beating or even execution as a part of military discipline and indeed Roman military discipline struck Polybius – himself an experienced Greek military man – as harsh (Polyb. 6.35-39).

In practice then, the ability of a magistrate to utilize imperium within Rome was hemmed in by the laws, whereas when out in the provinces on campaign it was far less limited. A second power, coercitio or ‘coercion’ – the power of a higher magistrate to use minor punishments or force to protect public order – is sometimes presented as a distinct power of the magistrates, but I tend to agree with Lintott (op. cit., 97-8) that this rather overrates the importance of the coercive powers of magistrates within the pomerium; in any case, the day-to-day maintenance of public order generally fell to minor magistrates.

While imperium was a ‘complete package’ as it were, the Romans clearly understood certain figures as having an imperium that outranked others, thus dictators could order consuls, who could order praetors, the hierarchy neatly visualized by the number of lictors each had. This could create problems, of course, when Rome’s informal systems of hierarchy conflicted with this formal system, for instance at the Battle of Arausio, the pro-consul Quintus Servilius Caepio refused to take orders from the consul, Gnaeus Mallius Maximus, because the latter was his social inferior (being a novus homo, a ‘new man’ from a family that hadn’t yet been in the Senate and thus not a member of the nobiles), despite the fact that by law the imperium of a sitting consul outranked that of a pro-consul. The result of that bit of insubordination was a military catastrophe that got both commanders later charged and exiled.

Finally, a vocabulary note: it would be reasonable to assume that the Latin word for a person with imperium would be imperator because that’s the standard way Latin words form. And I will say, from the perspective of a person who has to decide at the beginning of each thing I write what circumlocution I am going to use to describe “magistrate or pro-magistrate with imperium,” it would be remarkably fortunate if imperator meant that, but it doesn’t. Instead, imperator in Latin ends up swallowed by its idiomatic meaning of ‘victorious general,’ as it was normal in the republic for armies to proclaim their general as imperator after a major victory (which set the general up to request a triumph from the Senate). In the imperial period, this leads to the emperors monopolizing the term, as all of the armies of Rome operated under their imperium and thus all victory accolades belonged to the emperor. That in turn leads to imperator becoming part of the imperial title, from where it gives us our word ’emperor.’

That said, the circumlocution I am going to use here, because this isn’t a formal genre and I can, is ‘imperium-haver.’ I desperately wish I could use that in peer reviewed articles, but I fear no editor would let me (while Reviewer 2 will predictably object to ‘general’ ‘commander’ or ‘governor’ for all being modern coinages).

On to our first set of imperium-havers!


The six praetors are the junior imperium-possessing magistracy and though all of the praetors were elected together, by the Middle Republic the job of being praetor might vary quite a lot depending on which role you were assigned by the Senate. You will recall that the praetorship is an old office, originally taking the place of chief magistrate which later becomes the consulship (note Livy 3.5.11-12, 7.3.5-8; Cic. Leg. 3.8; Fest. 249L; Gell. 11.18.8, 20.1.47; Plin. NH 18.12 see also Varro Ling. 5.80), though at some point the title of the chief magistrate shifted being consul and the praetor (just one of them) served as a junior assistant to the consuls. We’re not well informed about the praetorship in this early form, but it seems likely it had a similar role in organizing the courts, while the consuls led the armies. In any case the number of praetors increases rapidly in the last half of the third century, with a second added in c. 242, two more in 228 and two more in 198/7, giving the total of six.

Because the praetors had imperium, they could in theory lead armies and organize courts the same as consuls (though they lacked some of the other distinctive consular powers we’ll discuss in a moment) but in practice the responsibilities of the praetors were usually quite distinct and split into two large categories: praetors assigned a provincia (which again, you should read as ‘job’ not ‘province’) at Rome and praetors assigned a provincia outside of Rome.

The two praetors operating normally in Rome were terms the praetor urbanus and praetor peregrinus and their responsibility was almost entirely focused on the court system. The praetor urbanus was primarily concerned with legal disputes involved two citizen parties, while any issue involving foreigners came under the jurisdiction of the praetor peregrinus, though the latter was sometimes also deployed out of Rome on special duties, at which point the praetor urbanus, who almost always remained in Rome, would handle both. On coming into office, the praetor urbanus (and probably also the praetor peregrinus) issued the edictum praetoris (‘Praetor’s edict’) which set out how he intended to carry out his office. Early on, these edicts seem mostly to have been restricted to changes in procedure or the assessment of damages, but by the first century praetorian edicts could lay out substantive law creating what later Roman jurists would term the ius praetorium (‘praetorian law’), which sat alongside the main law code itself, the ius civile (‘civil law’). Mostly what these edicts lay out seem to be procedures or the conditions under which the praetor will grant a cause of action. By the time the edict is fully developed, praetors seem to be seeking and getting advice from an emerging class of legal experts, iuris prudentes (‘men learned at law’ = ‘legal consult’) to craft what must often have been pretty formulaic edicts.

We’ll cover the Roman legal process towards the end of this series but we may cover the praetor’s role here in brief. When a case was raised – and Roman law understands all cases as disputes just like Greek law does, though unlike in most Greek poleis, some Roman magistrates seem to have had an expectation to act as quasi-public prosecutors for certain kinds of infractions – it was brought before the praetor, either urbanus for an issue involving citizens or peregrinus for an issue involving at least one non-citizen. At this point the matter was in iure (‘at law’) and the praetor held a sort of preliminary hearing to determine if there was a cause of action (thus the importance of this question in the praetor’s edict) and then to assign a judge (a iudex) who would administer the trial and to set a formula (formula, gotta love Latin), which functioned rather like jury instructions, naming the relevant parties, describing their dispute and setting out the consequences should the matter be ruled in favor of one or the other (this stage of the case is apud iudicem, ‘before a judge’). Note that the praetor doesn’t make a ruling, but merely lays out the formula.

For more serious matters that required a jury court to resolve, a potential prosecutor went before the praetor, who then assigned the case to the relevant court or assembly (as assemblies, especially early on, could act as courts) and set a date for the trial. Interestingly, for jury trials, no formula was provided by the praetor.

What about the praetors who weren’t assigned to Rome? As the sphere of Roman military activity expanded beyond Italy, it became necessary to have more commanders in the field, and this is where we get the additional praetors. Because a praetor has imperium, they can function as a sort of ‘mini-consul.’ That said, praetors don’t tend to get assigned the sorts of jobs consuls do. If Rome needs three major field armies, the Senate generally doesn’t send a praetor to command the third, rather it sends a pro-consul (which makes a degree of sense when you think about it; you want an experienced commander).

Instead, praetors in the field tend to be assigned to putative ‘quiet’ provinces or auxiliary support functions. The standard praetorian provinces were Corsica et Sardinia (one province) and Sicily, later joined by the two Spains (Hispania Citerior, ‘Nearer Spain’ and Hispania Ulterior, ‘Further Spain), when they were quiet. When a major military action flared up on this areas, the response wasn’t to send a praetor with a large army, but to assign a consul or a pro-consul to the province instead, though because these assignments are made annually that tends to mean that trouble flares up, the praetor with his smaller army tries to manage it and if he fails and is defeated, then a consul is sent out with a major army.

Now I don’t want to get entirely off-track detailing what a Roman commander does in his overseas provincia; I may add a supplemental post on this one describing what Roman provincial government looks like in the Republic (though for the curious, the book to read is F.K. Drogula, Commanders and Command (2015); it’s a bit dry, but quite thorough). But in brief a praetor in his overseas provincia is going to have command of whatever military forces are there, generally less than the standard two-legion consular army (sometimes a lot less!). If there is no active military campaign to be done, the praetor will transit around the province. Because he has imperium, he can resolve disputes as a court and in the provinces – because imperium is stronger outside of Rome – he can do so summarily so long as Roman citizens are not involved. He can enforce these resolutions on non-Romans in the province because he has a Roman army and the implicit backing of the rest of the Roman state. Note that the praetor in his province doesn’t take over day-to-day garden variety law and order issues; those are still handled by local governments, according to local laws.

Generally the expectation is that a praetor is going to use his mix of military force and his ability to resolve disputes and deliver judgements to keep good order in the region and to make sure that Rome’s taxes are collected. In practice within those confines, there’s a lot of latitude, though the Senate may make certain specific demands as part of a praetor’s assignment. The praetor is also assisted by an assigned quaestor who handles the financial side of things and is expected to consult a small council of advisors, a consilium, when making decisions. Finally, beginning in 149, there is a permanent court in Rome which has the job of handling the cases of governors who exceeded their mandate in the provinces, the quaestio de repetundis; the name literally means ‘the court for things you need to give back’ because the primary concern was governors extorting money and taking bribes in their provinces. So the praetor’s latitude is not infinite.

As the number of active provinciae became too large for even the larger number of praetors and the two consuls, the Senate took to having former praetors serve as ‘pro-praetors,’ a kind of pro-magistrate, but we’ll talk about them below, after we’ve discussed the most important Roman magistrate, the consuls.

The Consuls

The consuls, always a pair, are the senior magistrates of the Roman Republic. While the censors, if there are any in office, may be themselves senior consulars (that is, ex-consuls), the sitting consuls are still the most powerful magistrates. Consuls wield imperium, but of a greater degree than any other magistrate or pro-magistrate (save a dictator), allowing them to in theory give orders to other magistrates (though this doesn’t happen often). The consuls also lead Rome’s primary field armies through the Middle Republic (this shifts only with Sulla’s reforms in 83).

While in theory the consuls’ possession of imperium meant they could superintend the courts, they generally didn’t (some Late Republic exceptions, like Pompey presiding over the trial of Titus Annius Milo are remarkable for being unusual). Instead, we most often see consuls in two roles: moving major legislation and leading Rome’s main field armies. In the former case, technically the praetors could legislate as well as the consuls, but in practice major laws tended to be proposed by either the consuls or the plebeian tribunes.

Each consul would also command a major field army. The Romans do not do army-command-by-committee (unlike Athens), so under normal circumstances the consuls each had independent command over their own army. The standard strength of a consular army was two legions (8,400 infantry, 600 cavalry) plus two alae of socii (varies but roughly the same size, with somewhat more cavalry), meaning that each consul in the Middle Republic goes to war with a chunky c. 20,000 man army. It was only in rare circumstances that these armies would be combined and such combined ‘double consular’ armies often caused problems if the consuls couldn’t get along or agree on a strategic vision.

That said, how many troops a consul might have and where he would be expected to take them was largely determined by the Senate. The Senate, as we’ll see, assigns provincia (again, think ‘jobs’ not ‘provinces’) – even to the consuls – and it also directs the quaestors on how resources are to be allocated. That includes conscription (the dilectus) and we see repeatedly that consuls do not feel they can hold a dilectus without the consent of the Senate; they can take volunteers without senatorial approval, but a draft, no. Likewise, unless they can find volunteer funding, they are reliant on quaestors releasing funds, quaestors who are always going to do what the Senate tells them to do.

However, the Senate can’t come on campaign with the consuls and so once in the field, dealing with whatever problem the Senate has suggested they deal with, the consuls have a great deal of command independence and nearly limitless authority. Whereas at Rome consular authority is constrained by laws and the plebeian tribunes (whose powers end at the pomerium), in the field they can implement strict military discipline and command their armies as they see fit. That extends to considerable latitude when it comes to negotiating with foreign states (neutral or hostile), though any treaty they make must be ratified back in Rome (technically requiring approval of an assembly but in practice this depends on if the Senate approves).

Now with such sweeping powers the Romans were naturally concerned that the consuls might usurp the state, so they instituted a few basic checks on this. One of these checks is simply the existence of the plebeian tribunes, but we’ll talk about those next time. But also it was clearly established that there must always be two consuls. Not one, not three. Two. If one consul dies, another must be immediately elected; this replacement consul was called a consul suffectus (the year was still dated from the two consuls elected at the beginning, the consules ordinarii). Because only a consul had the authority to hold a consular election, you needed a system to handle situations where both consuls were indisposed at once (either both dead or one dead and one abroad with the army); the solution was a rare official, the interrex, who only had the authority to hold an election for the consulship.

Once you’ve ensured there are always two consuls, the next trick is to make sure they can check each other. To ensure that, consuls were given some substantial powers. The most famous of these was veto, Latin for “I forbid!” Just by saying the word, a consul could block any action by any other magistrate, including the other consul. The power had to be exercised in person, which limited it: if you really wanted to prevent your colleague from doing something he really wanted to do, you best be prepared to follow him around in person every day to keep vetoing it. A supercharged for of veto consuls could also exercise was iustitium, declaring a stop to all state business; this could be used to stop any meeting of a popular assembly or of the Senate so long as the assembly had not dispersed into voting groups.

The final check on the consuls is pretty simple: they only serve for one year. After which it is generally expected that there be a respectable interval (usually around 10 years) before you can run for the consulship again. While in office, any Roman with imperium is immune from prosecution, but can be prosecuted immediately on leaving office for any crimes they may have done while in office. Consequently, a consul’s freedom of action is going to be limited by their concern about potentially having to face a jury after their one-year term is complete. Even if they aren’t worried about that, once their year is done they go back to being just another senator, so good relations with the rest of the Senate is a good idea.

In part because one of the other things the Senate decides on are…


Roman expansion put strains on all of these systems. Fundamentally, the Roman system remained one designed for a small city-state. Everything – military command, attending the Senate, passing legislation, using veto power – needed to be done in person by magistrates who only had a single year in office. While Roman territory and the scope of Rome’s wars remained small, that sort of system worked fine. As Roman territory and Rome’s wars expanded, it put all sorts of strains on that system: how to handle multi-year campaigns which kept the armies in the field? How to handle having more commands than magistrates?

The solution was to extend (prorogue) a magistrate’s authority, making them a pro-magistrate (‘pro’ meaning ‘standing in for’). It’s tricky to pin down exactly when the Romans first did this as our sources for early Rome (Livy and Dionysius of Halicarnassus) tend to use terms for proconsular power (pro consule or ἀνθύπατον ἀρχὴν) long before prorogation seems to have been used in Rome. Generally, we think that the first genuine prorogation happens in 327 as part of the run-up to the Second Samnite War (Livy 8.23). The problem here was two-fold: Rome’s evident shift to year-round campaigning meaning that the army needed a continous commander in the field as in this case where it was conducting a siege, combined with the greater distances – the commander, Q. Pubilius Philo, is besieging Naples – making swift changes in command difficult.

Prorogation becomes common and regular during the Punic Wars. The First Punic War, taking place primarily in Sicily, demanded the use of prorogation to cover the lag time between elections in Rome and commanders arriving in Sicily, as well as to allow single commanders to conduct more complex campaigns. By the Second Punic War, which takes place in Italy, Sicily, Gaul, Spain, North Africa and Illyria (much of that simultaneously) it was also necessary to prorogue commanders in order to simply get enough field commanders with imperium for all of the armies Rome was deploying. Indeed, in the crazy days of the Second Punic War, at points the Senate prorogued men who had never held office before, privati cum imperio (private citizens with imperium), though this is discontinued and replaced by a system whereby prorogued commanders will have first held the relevant office at some point.

The expanding number of areas of Roman overseas control pushed this further as more regions meant more provinciae (in the sense of ‘jobs’) which demanded more imperium-havers to handle. New praetors were eventually made for Sicily, Corsica-and-Sardinia and the two Spains, but by the mid-second century the Romans are regularly assigning imperium-havers to Gaul (Cisalpine or Transalpine), Africa, Greece and Macedonia and of course also need magistrates with imperium in Italy to handle the regular functions of government.

One of the pressures here is that by this point it was clearly locked into tradition that there were only ever two consuls. It had not always been that way; back when the Romans had military tribunes with consular powers, they had three of them. But by the third century, there were always and could only be two consuls. But that’s a problem because even if you have spare praetors, you don’t assign praetors to major military commands, so if you have three major military commands, you don’t send a praetor, you assign a proconsul.

The result of all of this is that each year the most pressing military problems generally got a consul assigned to them. Often the military problem from last year that was on-going would see its ex-consul prorogued to continue handling it. Likewise, the new praetors would be sent out to replace the governors in quiet provinces, with the remainder who weren’t replaced prorogued to hold down the fort for another year. Later it is going to become quite common for former praetors and consuls who had returned to Rome to be dispatched back out to the provinces to do a stint as a promagistrate, but the common use of this is really a consequence of the Sullan reforms and for the most part belongs to the first century. Most third and second century promagistrates are having an existing command extended rather than being sent out fresh.

Extensions of this sort, I should note, were generally fairly short. The longest run I can think of in this period is that of Publius Cornelius Scipio Africanus who is privati cum imperio pro consule (‘private citizen with pro-consular imperium’) from 210 to 206, mostly as a product of his father and uncle having been the local Roman commanders in Spain and Scipio having taken over when they were both killed, leading to an irregular, emergency command. He’s then consul in 205, before having his command prorogued from 204 to 201 to complete his invasion of Africa (technically, he’s assign to Sicily with permission to invade Africa if an opportunity presented itself).

Far more typical for even an exceptional commander was something like Scipio Aemilianus’ experience. Consul in 147, he is prorogued to complete the destruction of Carthage in 146. Then, consul in 134, he is prorogued to complete the destruction of Numantia in 133. And that was that. The point here being that the heavy reliance on proconsuls to conduct the main effort in Roman wars, often with longer commands (most famously Caesar’s eight years in Gaul or Pompey’s back-to-back eastern commands from 67 to 62) visible in the Late Republic was not common practice in the Middle Republic.

One significant legal quirk of prorogation is that while a consul or a praetor at least notionally had imperium which traveled (though in practice they would be expected to focus on the provincia the Senate assigned them), the imperium of a promagistrate, who after all only ‘stood in for’ the actual magistrate of the year, was in fact restricted to their defined sphere of action.

My plan once we’ve gone through the whole Roman system for Romans is to add two more posts on this series (perhaps not coming right away), one covering how the Roman Republic interacts with the socii and another briefly describing the shape of Roman governance in the provinces But for now, that’s enough on imperium. Next week, we’re going to look at two very strange major offices, the tribunate and the censorship, plus discuss what we know of the key minor offices of the republic.

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