Magister equitum in the context of "Roman cavalry"

In ancient Rome, imperium was a form of authority held by a citizen to control a military or governmental entity. It is distinct from auctoritas and potestas, different and generally inferior types of power in the Roman Republic and Empire. One's imperium could be over a specific military unit, or it could be over a province or territory. Individuals given such power were referred to as curule magistrates or promagistrates. These included the curule aedile, the praetor, the consul, the magister equitum, and the dictator. In a general sense, imperium was the scope of someone's power, and could include anything, such as public office, commerce, political influence, or wealth.

Marcus Aemilius Lepidus (/ˈlɛpɪdəs/; c. 89 BC – late 13 or early 12 BC) was a Roman general and statesman who formed the Second Triumvirate alongside Octavian and Mark Antony during the final years of the Roman Republic. Lepidus had previously been a close ally of Julius Caesar. He was also the last pontifex maximus before the Roman Empire, and (presumably) the last interrex and magister equitum to hold military command.

Though he was an able military commander and proved a useful partisan of Caesar, Lepidus has always been portrayed as the least influential member of the Triumvirate. He typically appears as a marginalised figure in depictions of the events of the era, most notably in Shakespeare's plays. While some scholars have endorsed this view, others argue that the evidence is insufficient to discount the distorting effects of propaganda by his opponents, principally Cicero and, later, Augustus.

Count Theodosius (Latin: Theodosius comes; died 376), Flavius Theodosius or Theodosius the Elder (Latin: Theodosius major), was a senior military officer serving Valentinian I (r. 364–375) and the Western Roman Empire during Late Antiquity. Under his command the Roman army defeated numerous threats, incursions, and usurpations. Theodosius was patriarch of the imperial Theodosian dynasty (r. 379–457) and father of the emperor Theodosius the Great (r. 379–395).

Appointed comes rei militaris per Britannias (commander of mobile military forces for the Diocese of the Britains) by Valentinian, Theodosius put down the Great Conspiracy (367–368) and the usurpation of Valentinus. After restoring order in Britain he returned to continental Europe and fought against the Alemanni; as Valentinian's magister equitum (Master of Horse) he successfully invaded Alemannic territory (371 or 370). In 372 Theodosius led a successful campaign against the Sarmatians. Within the same year Firmus, a Mauritanian prince, rebelled against Roman rule with the help of African tribes like the Abanni and Caprarienses. Theodosius was sent to Africa and in two hard-fought campaigns (373–374) put down the insurrection. In 376, after the death of emperor Valentinian, he was arrested and executed, presumably as he was seen as a threat to the new western emperors Gratian and Valentinian II.

The celeres (Latin: [ˈkɛɫ̪ɛre:s], Ancient Greek: κελέριοι) were the bodyguard of the kings of Rome and the earliest cavalry unit in the Roman military. Traditionally said to have been established by Romulus, the legendary founder and first King of Rome, the celeres comprised three hundred men, ten chosen by each of the curiae. The celeres were the strongest and bravest warriors among the early Roman nobility, and were the bravest and most loyal soldiers in the army. The celeres may also have originated in the fourth century BC when the Romans adopted cavalry from the Samnites. The name of celeres was generally believed to have arisen from their celeritas, or swiftness, but Valerius Antias maintained that their first commander was named "Celer", perhaps the same Celer mentioned by Ovid as the foreman of the first fortification built around the Palatine Hill; it was he, rather than Romulus himself, who slew Remus after he overleapt the wall. According to some accounts they were infantry; while according to others they included both or were only cavalry.

Unlike most soldiers of the period, who served only in times of war, the celeres were a permanent force, attending the king at all times, including times of peace. They are generally regarded as a cavalry unit, for the Roman kings traveled and fought on horseback, and in his absence the celeres were led by the tribunus celerum, or tribune of the celeres, who doubled as the king's lieutenant and head of the royal household, holding a position analogous to that of the magister equitum under the Roman Republic. However, Dionysius of Halicarnassus states that the celeres fought mounted only where the ground was favourable, dismounting to fight on foot where the ground was unsuitable for cavalry. Numa Pompilius, the second King of Rome, established certain religious rites that the commanders of the celeres were required to perform.

The executive magistrates of the Roman Empire were elected individuals of the ancient Roman Empire. During the transition from monarchy to republic, the constitutional balance of power shifted from the executive (the Roman King) to the Roman Senate. During the transition from republic to empire, the constitutional balance of power shifted back to the executive (the Roman Emperor). Theoretically, the senate elected each new emperor, although in practice, it was the army which made the choice. The powers of an emperor, (his imperium) existed, in theory at least, by virtue of his legal standing. The two most significant components to an emperor's imperium were the "tribunician powers" (potestas tribunicia) and the "proconsular powers" (imperium proconsulare). In theory at least, the tribunician powers (which were similar to those of the Plebeian Tribunes under the old republic) gave the emperor authority over Rome's civil government, while the proconsular powers (similar to those of military governors, or Proconsuls, under the old republic) gave him authority over the Roman army. While these distinctions were clearly defined during the early empire, eventually they were lost, and the emperor's powers became less constitutional and more monarchical.

Under the empire, the citizens were divided into three classes, and for members of each class, a distinct career path was available (known as the cursus honorum). The traditional magistracies were only available to citizens of the senatorial class. The magistracies that survived the fall of the republic were (by their order of rank in the cursus honorum) the Consulship, Praetorship, Plebeian Tribunate, Aedileship, Quaestorship, and Military Tribunate. If an individual was not of the senatorial class, he could run for one of these offices if he was allowed to run by the emperor, or otherwise, he could be appointed to one of these offices by the emperor. Mark Antony abolished the offices of Roman Dictator and Magister equitum ("Master of the Horse") during his Consulship in 44 BC, shortly after the assassination of Julius Caesar. The office of Interrex was also abolished during the transition from republic to empire. In 22 BC the emperor Augustus appointed P. Aemilius Lepidus and L. Munatius Plancus to the Censorship, and while they began a census that year, they never completed it, and shortly thereafter the office was abolished. The emperor Claudius attempted to revive the office by appointing himself and L. Vitellius Censor in 47 AD, but after Claudius, no further attempts were made to revive the office.

Gaius Junius Bubulcus Brutus (fl. late 4th century BC) was a Roman general and statesman, he was elected consul of the Roman Republic thrice, he was also appointed dictator or magister equitum thrice, and censor in 307 BC. In 311, he made a vow to the goddess Salus that he went on to fulfill, becoming the first plebeian to build a temple. The temple was one of the first dedicated to an abstract deity, and Junius was one of the first generals to vow a temple and then oversee its establishment through the construction and dedication process.

The desultory manner in which Junius Bubulcus survives in the historical record obscures the stature indicated by the number of high offices he held from 317 to 302 BC; it has been observed that he "cannot have been as colourless as he appears in Livy."