The prorogatio imperium positions, which are the pro-consul and pro-praeter, were established in 326 BC as military positions to aid the military needs of the Consuls. This places them in the Roman middle republic and is probably a result of Rome's expansion during that period placing pressure on military and civil administration in the provinces.

The position of Consul was a civil one in Rome, but outside of Rome it was a military position. So consular prestige came from military campaigns - a triumph, which was a parade through Rome to celebrate a military victory, was essential for the political popularity of any aspirant public figure. Whether a triumph would be held was up to the Senate who would vote on such measures - meaning the Senate could control who received triumphs, but also, it made it impossible for them to vote down a triumph for a truly popular general.

The praetor was a position that was established during the middle republic as well, in 366 BC. The praetor was intended to be a consul, who was restricted to civil affairs in the city. Scullard writes that this position was created as a patrician only one after plebians became eligible for the Consulship, but notes that by 337 BC plebians became eligible for this magistrate position.

The pro-consul and pro-praetar were the prior term's consuls and praetors who were given imperium in the provinces after they had finished their elected term in the magistracy. This certainly did make the position of Consul powerful, as imperium continued with the prorogatio positions. In later years the provinces were used by former consuls and praetors to pay for all the bribery they had done the year before in order to get elected.

Andrew Lintott writes that the territories the pro-consuls and pro-praetors had imperium were massive even by today's standards; and meant that the military and economic power of Rome was in the hands of the pro-consuls and pro-praetors.

Moreover, the growth of Roman military power and empire, which ultimately allowed a single Roman commander discretion over territory which in the present day forms more than one nation-state, made the powers of a consul in Rome insignificant compared with those of a consul or proconsul abroad.

In the late republic and its political turmoil, pro-consuls were a source of constant consternation and pro-consuls preferred the pro-consulship of Cisalpine Gaul as it placed their military just north of Rome, close by in case of any political development for or against them. When the Senate went after Mark Antony with Octavian, Pansa and Hirtius; Antony was just north of Italy.