The Roman republic is a phase of the civilization of ancient Rome which began in 509 BC. J.-C., after the fall of the monarchy. Empire controled approximately 5 900 000 sq km of land surface and 88 million citizens, of whom more than a million and half in the city of Rome, and about one million soldiers.
SPQR presents government of the ancient Roman Republic, and been used as an official signature of the government. Political control belonged to the few elite, rich, and powerful persons and influential families. The Senate represented the aristocratic and elitist element of Roman government and was a collection of patrician citizens, who served as the legislative branch of the government as well as an advisory body.
In the beginning of the Republic, the Senate contained 300 members, the members themselves were chosen from the patrician class, ex-consuls, and other officers who served for life. Despite having a mostly advisory role, by the 3rd Century BC the Senate had been able to increase its influence and power. Some of the powers that it gained were that it prepared legislation to be put before the Assembly, it administered finances, dealt for foreign affairs, and supervised the official state religions. However, despite its increase in power, the Senate did not have the power to make laws, by only issue decrees known as Decreta or Senatus Consulta, which basically served as official recommendations and while they carried some weight, they still had no actual binding and legal authority.
Meetings of the Senate were attended by the Senators themselves and magistrates (the consul for example) only. However, the public could gather by the open doors of the Senate. The meetings took place in the Curia Hostilia in the northwest corner of the Forum, but they could take place at any public place within the city limits of Rome.
The Senate met daily, and Senators were allowed to address the Senate on matters pertaining to state or foreign affairs. In fact, a main activity of the Senate was the debate of issues and many of the early senators were great orators and we have their words preserved for us today by contemporary historians. Cato the Censor, Cicero, and others sometimes swayed the opinion of the entire population of Rome with their fine rhetoric and persuasive arguments.
SPQR is an initialism from latin phrase Senatus Populus que Romanus, which means The Senate and the Roman People. It appears on coins, at the end of documents made public by inscription in stone or metal, in dedications of monuments and public works and was emblazoned on the standards of the Roman legions. Legions were standing units, which could remain in being for several years, or even decades. This became necessary to garrison the Republic's now far-flung territories. Legionaries started large-scale recruiting of volunteer soldiers enlisted for a minimum term of six years and a fixed salary, although conscription was still practised. The property requirements, already much reduced, seem to have been abolished, so the bulk of recruits were henceforth from the landless proletariat, who would be most attracted to the paid employment offered by the legions.
In the last century of the Republic, proconsuls governing frontier provinces became increasingly powerful. Their command of standing legions in distant and arduous military campaigns resulted in the allegiance of those units transferring from the Roman state to themselves. Large numbers of new legions were raised by rival warlords for the civil wars of the period 49-30 BC.
However, when Augustus became sole ruler in 30 BC, he disbanded about half the over 50 legions then in existence. The remaining 28 legions became the core of the early Imperial army, most lasting over three centuries. Augustus and his immediate successors transformed legions into permanent units, staffed by entirely career soldiers on standard 25-year terms.
Wikipedia : "The Roman people appear very often in law and history in such phrases as dignitas, maiestas, auctoritas, libertas populi Romani, the "dignity, majesty, authority, freedom of the Roman people." They were a populus liber, "a free people." There was an exercitus, imperium, iudicia, honores, consules, voluntas of this same populus: "the army, rule, judgements, offices, consuls and will of the Roman people". They appear in early Latin as Popolus and Poplus, so the habit of thinking of themselves as free and sovereign was quite ingrained. "[]
Rome's influence in culture, laws, technology, government, arts, language or religion on the civilizations that succeeded endures till today, same as Roman army. Due to the enormous military successes of the Roman Republic and the Roman Empire the legion has long been regarded as the prime ancient model for military efficiency and ability.
With admiration for such a discipline and organization here is the map of ancient Roman Empire.