Romans considered the consulship the second-highest level of the cursus honorum—an ascending sequence of public offices to which politicians aspired—after that of the censor, which was reserved for former consuls.
The practice of dual leaders (diarchy) continues to this day in San Marino and is directly derived from the customs of the Roman Republic.
[3] The consulship was believed by the Romans to date back to the traditional establishment of the Republic in 509 BC, but the succession of consuls was not continuous in the 5th century BC, when the consulship was supposedly replaced with a board of consular tribunes, which was elected whenever the military needs of the state were significant enough to warrant the election of more than the usual two consuls.
[6] Consuls had extensive powers in peacetime (administrative, legislative, and judicial), and in wartime often held the highest military command.
Additional religious duties included certain rites which, as a sign of their formal importance, could only be carried out by the highest state officials.
[11][12] Beginning in the late Republic, after finishing a consular year, a former consul would usually serve a lucrative term as a proconsul, the Roman governor of one of the senatorial provinces.
It would not be uncommon for the patrician consuls of the early Republic to intersperse public office with agricultural labor.
[13] In Cicero's words: in agris erant tum senatores, id est senes:[14] 'In those days senators—that is, seniors—would live on their farms'.
Although throughout the early years of the Principate the consuls were still formally elected by the comitia centuriata, they were de facto nominated by the princeps.
During reigns of the Flavian and Antonine emperors, the ordinary consuls tended to resign after a period of four months, and the elections were moved to 12 January of the year in which they were to hold office.
[17] However, the high regard placed upon the ordinary consulate remained intact, as it was one of the few offices that one could share with the emperor, and during this period it was filled mostly by patricians or by individuals who had consular ancestors.
[23] Consequently, holding the ordinary consulship was a great honor and the office was the major symbol of the still relatively republican constitution.
[23] This had the effect of seeing a suffect consulship granted at an earlier age, to the point that by the 4th century, it was being held by men in their early twenties, and possibly younger, without the significant political careers behind them that was normal previously.
By that time, the Greek titles for consul and ex-consul, "hypatos" and "apo hypaton", had been transformed to relatively lowly honorary dignities.
While the rex sacrorum inherited the kings' position as royal priest and various religious functions were handed off to the pontiffs, the consuls were given the remaining civil and military responsibilities.
To prevent abuse of the kingly power, this authority was shared by two consuls, each of whom could veto the other's actions, with short annual terms.
In the gradual development of the Roman legal system, however, some important functions were detached from the consulship and assigned to new officers.
As long as the consuls were in the pomerium (the city of Rome), they were at the head of government, and all the other magistrates, with the exception of the tribune of the plebs, were subordinate to them, but retained independence of office.
As part of their executive functions, the consuls were responsible for carrying into effect the decrees of the Senate and the laws of the assemblies.
Each consul was accompanied in every public appearance by twelve lictors, who displayed the magnificence of the office and served as his bodyguards.
[33] When inside the pomerium, the lictors removed the axes from the fasces to show that a citizen could not be executed without a trial.
Upon entering the comitia centuriata, the lictors would lower the fasces to show that the powers of the consuls derive from the people.
Each consul commanded an army, usually two legions strong, with the help of military tribunes and a quaestor who had financial duties.
In the early years of the Republic, Rome's enemies were located in central Italy, so campaigns lasted a few months.
[35] So the consul upon entering office was expected by the Senate and the People to march his army against Rome's enemies, and expand the Roman frontiers.
However, after the campaign, he could be prosecuted for his misdeeds (for example for abusing the provinces, or wasting public money, as Scipio Africanus was accused by Cato in 205 BC).
In order to avoid unnecessary conflicts, only one consul would actually perform the office's duties every month and could act without direct interference.
Another point which acted as a check against consuls was the certainty that after the end of their term they would be called to account for their actions while in office.
In times of crisis, when Rome's territory was in immediate danger, a dictator was appointed by the consuls for a period of no more than six months, after the proposition of the Senate.
In Latin, the ablative absolute construction is frequently used to express the date, such as "M. Messalla et M. Pupio Pisone consulibus", translated literally as "With Marcus Messalla and Marcus Pupius Piso (being) the consuls", with 'being' implied, as it appears in Caesar's De Bello Gallico.