Magister equitum

The magister equitum, in English master of the horse or master of the cavalry, was a Roman magistrate appointed as lieutenant to a dictator. His nominal function was to serve as commander of the Roman cavalry in time of war, but just as a dictator could be nominated to respond to other crises, so the magister equitum could operate independently of the cavalry; like the dictator, the appointment of a magister equitum served both military and political purposes.

Origin

In the time of the Roman Kingdom, the king himself would lead the cavalry into battle, or else delegate this authority to his chief advisor, the Tribune of the Celeres, the cavalry unit that also served as the king's personal bodyguard. The last person to hold this position was Lucius Junius Brutus, nephew of Lucius Tarquinius Superbus, the seventh and final King of Rome. After the rape of Lucretia, it was Brutus who, in his capacity as Tribune of the Celeres, convened the comitia, and brought about the abrogation of the king's imperium. Following the expulsion of Tarquin, Brutus, whom the comitia elected one of the first consuls, commanded the cavalry in the Battle of Silva Arsia, where he fell, BC 509.

In the early years of the Republic, no attempt was made to reconstitute the office of Tribune of the Celeres; the supreme military authority was vested in the consuls. In keeping with the principle that no one man should hold the full power of the Roman state, it was possible to appeal the decisions of one consul to the other. However, in the ninth year of the Republic, war appeared imminent with both the Latin League, led by the exiled king's son-in-law, Octavius Mamilius, and the Sabines, with whom the Romans had fought in 505 and 503 BC. At the same time, there was suspicion that the consuls harbored royalist sympathies. In the face of this panic, the Romans resolved to appoint a praetor maximus, or dictator, as the office came to be called, from whom there should be no right of appeal, for the duration of the emergency.