Roman Senate in the context of "Roman Kingdom"

The Roman Republic (Latin: Res publica Romana [ˈreːs ˈpuːblɪka roːˈmaːna]) was the era of classical Roman civilisation beginning with the overthrow of the Roman Kingdom (traditionally dated to 509 BC) and ending in 27 BC with the establishment of the Roman Empire following the War of Actium. During this period, Rome's control expanded from the city's immediate surroundings to hegemony over the entire Mediterranean world.

Roman society at the time was primarily a cultural mix of Latin and Etruscan societies, as well as of Sabine, Oscan, and Greek cultural elements, which is especially visible in the ancient Roman religion and its pantheon. Its political organisation developed at around the same time as direct democracy in ancient Greece, with collective and annual magistracies, overseen by a senate. There were annual elections, but the republican system was an elective oligarchy, not a democracy, with a number of powerful families largely monopolising the senior magistracies. Roman institutions underwent considerable changes throughout the Republic to adapt to difficulties such as the creation of promagistracies to rule its conquered provinces and, after the Social War during the late Republic, the inclusion of peninsular Italians as citizens and senators.

During the classical period, the Roman Empire controlled the Mediterranean and much of Europe, Western Asia, and North Africa. The Romans conquered most of these territories in the time of the Republic, and it was ruled by emperors following Octavian's assumption of power in 27 BC. Over the 4th century AD, the empire split into western and eastern halves. The western empire collapsed in 476 AD, while the eastern empire endured until the fall of Constantinople in 1453.

By 100 BC, the city of Rome had expanded its rule from the Italian peninsula to most of the Mediterranean and beyond. However, it was severely destabilised by civil wars and political conflicts, which culminated in the victory of Octavian over Mark Antony and Cleopatra at the Battle of Actium in 31 BC, and the subsequent conquest of the Ptolemaic Kingdom in Egypt. In 27 BC, the Roman Senate granted Octavian overarching military power (imperium) and the new title of Augustus, marking his accession as the first Roman emperor. The vast Roman territories were organized into senatorial provinces, governed by proconsuls who were appointed by lot annually, and imperial provinces, which belonged to the emperor but were governed by legates.

Marcus Porcius Cato (/ˈkɑːtoʊ/, KAH-toe; 234–149 BC), also known as Cato the Censor (Latin: Censorius), the Elder and the Wise, was a Roman soldier, senator, and historian known for his conservatism and opposition to Hellenization. He was the first to write history in Latin with his Origines, a now fragmentary work on the history of Rome. His work De agri cultura, a treatise on agriculture, rituals, and recipes, is the oldest extant prose written in the Latin language. His epithet "Elder" distinguishes him from his great-grandson Senator Cato the Younger, who opposed Julius Caesar.

He came from an ancient plebeian family who were noted for their military service. Like his forefathers, Cato was devoted to agriculture when not serving in the army. Having attracted the attention of Lucius Valerius Flaccus, he was brought to Rome. He was successively military tribune (214 BC), quaestor (204), aedile (199), praetor (198), consul (195) together with Flaccus, and censor (184). As praetor, he expelled usurers from Sardinia. As censor, he tried to save Rome's ancestral customs and combat Hellenistic influences.

The War of Actium (32–30 BC) was the last civil war of the Roman Republic, fought between Mark Antony (assisted by Cleopatra and by extension Ptolemaic Egypt) and Octavian. In 32 BC, Octavian convinced the Roman Senate to declare war on the Egyptian queen Cleopatra. Her lover and ally Mark Antony, who was Octavian's rival, gave his support for her cause. Forty percent of the Roman Senate, together with both consuls, left Rome to join the war on Antony's side. After a decisive victory for Octavian at the Battle of Actium, Cleopatra and Antony withdrew to Alexandria, where Octavian besieged the city until both Antony and Cleopatra were forced to commit suicide.

The war involved some of the largest Roman armies ever seen. Both Antony and Octavian's legions were experienced veterans of previous civil wars who had fought together, many also having once served under Julius Caesar. The two did however raise their own legions separately.

The constitutional reforms of Augustus were a series of laws that were enacted by the Roman Emperor Augustus between 30 BC and 2 BC, which transformed the Constitution of the Roman Republic into the Constitution of the Roman Empire. The era during which these changes were made began when Augustus defeated Mark Antony and Cleopatra at the Battle of Actium in 31 BC, and ended when the Roman Senate granted Augustus the title "Pater Patriae" in 2 BC.

The history of the Roman Empire covers the history of ancient Rome from the traditional end of the Roman Republic in 27 BC until the abdication of Romulus Augustulus in AD 476 in the West, and the Fall of Constantinople in the East in 1453. Ancient Rome became a territorial empire while still a republic but was then ruled by emperors, beginning with Octavian Augustus, the final victor of the republican civil wars.

Rome had begun expanding shortly after the founding of the Republic in the 6th century BC, though it did not expand outside the Italian Peninsula until the 3rd century BC, during the Punic Wars, after which the Republic expanded across the Mediterranean. Civil war engulfed Rome in the mid-1st century BC, first between Julius Caesar and Pompey, and finally between Octavian (Caesar's grand-nephew) and Mark Antony. Antony was defeated at the Battle of Actium in 31 BC, leading to the annexation of Egypt. In 27 BC, the Senate gave Octavian the titles of Augustus ("venerated") and Princeps ("foremost"), thus beginning the Principate, the first epoch of Roman imperial history. Augustus' name was inherited by his successors, as well as his title of Imperator ("commander"), from which the term "emperor" is derived. Early emperors avoided any association with the ancient kings of Rome, instead presenting themselves as leaders of the Republic.

Primus inter pares is a Latin phrase meaning first among equals. It is typically used as an honorary title for someone who is formally equal to other members of their group but is accorded unofficial respect, traditionally owing to their seniority in office.

Historically, the princeps senatus of the Roman Senate was such a figure and initially bore only the distinction that he was allowed to speak first during debate. After the fall of the Republic, Roman emperors initially referred to themselves only as princeps despite having enormous power.

Trajan (/ˈtreɪdʒən/ TRAY-jən; born Marcus Ulpius Traianus, 18 September 53 – c. 9 August 117) was a Roman emperor from AD 98 to 117, remembered as the second of the Five Good Emperors of the Nerva–Antonine dynasty. He was a philanthropic ruler and a successful soldier-emperor who presided over one of the greatest military expansions in Roman history, during which, by the time of his death, the Roman Empire reached its maximum territorial extent. He was given the title of Optimus ('the best') by the Roman Senate.

Trajan was born in the municipium of Italica in the present-day Andalusian province of Seville in southern Spain, an Italic settlement in Hispania Baetica; his gens Ulpia came from the town of Tuder in the Umbria region of central Italy. His namesake father, Marcus Ulpius Traianus, was a general and distinguished senator. Trajan rose to prominence during the reign of Domitian; in AD 89, serving as a legatus legionis in Hispania Tarraconensis, he supported the emperor against a revolt on the Rhine led by Antonius Saturninus. He then served as governor of Germania and Pannonia. In September 96, Domitian was succeeded by the elderly and childless Nerva, who proved to be unpopular with the army. After a revolt by members of the Praetorian Guard, Nerva decided to adopt as his heir and successor the more popular Trajan, who had distinguished himself in military campaigns against Germanic tribes.