Roman Empire

===Transition from Republic to Empire===
{{Further|Roman Republic}}
[[File:Augustus of Prima Porta (inv. 2290).jpg|thumb|upright|''[[Augustus of Prima Porta]]'']]
Rome had begun expanding shortly after the founding of the [[Roman Republic]] in the 6th century BC, though not outside the Italian peninsula until the 3rd century BC. Thus, it was an "empire" (a great power) long before it had an emperor.<ref>{{Harvp|Kelly|2007|pp=4ff}}; {{Harvp|Nicolet|1991|pp=1, 15}}; {{Cite book |last=Brennan |first=T. Corey |title=The Praetorship in the Roman Republic |date=2000 |publisher=Oxford University Press |page=605 |author-link=T. Corey Brennan}} {{Harvp|Peachin|2011|pp=39–40}}</ref> The Republic was not a nation-state in the modern sense, but a network of self-ruled towns (with varying degrees of independence from the [[Roman Senate|Senate]]) and provinces administered by military commanders. It was governed by annually elected [[Roman magistrate|magistrates]] ([[Roman consul]]s above all) in conjunction with the Senate.{{Sfnp|Potter|2009|p=179}} The 1st century BC was a time of political and military upheaval, which ultimately led to rule by emperors.{{Sfnp|Nicolet|1991|pp=1, 15}}<ref name=Hekster/><ref>{{Cite book |last=Lintott |first=Andrew |title=The Constitution of the Roman Republic |date=1999 |publisher=Oxford University Press |page=114 |author-link=Andrew Lintott}}; {{Cite book |last=Eder |first=W. |chapter=The Augustan Principate as Binding Link |date=1993 |title=Between Republic and Empire |publisher=University of California Press |isbn=0-520-08447-0 |page=98}}</ref> The consuls' military power rested in the Roman legal concept of ''[[imperium]]'', meaning "command" (though typically in a military sense).<ref>{{Cite book |last=Richardson |first=John |chapter=Fines provincial |date=2011 |title=Frontiers in the Roman World |publisher=Brill |page=10}}</ref> Occasionally, successful consuls were given the honorary title ''[[imperator]]'' (commander); this is the origin of the word ''emperor'', since this title was always bestowed to the early emperors.{{Sfnp|Richardson|2011|pp=1–2}}

Rome suffered a long series of internal conflicts, conspiracies, and [[Roman civil wars|civil wars]] from the late second century BC (see [[Crisis of the Roman Republic]]) while greatly extending its power beyond Italy. In 44 BC [[Julius Caesar]] was briefly ''[[Roman dictator|dictator]]'' before being [[Assassination of Julius Caesar|assassinated]]. The faction of his assassins was driven from Rome and defeated at the [[Battle of Philippi]] in 42 BC by [[Mark Antony]] and Caesar's adopted son [[Augustus|Octavian]]. Antony and Octavian's division of the Roman world did not last and Octavian's forces defeated those of Mark Antony and [[Cleopatra]] at the [[Battle of Actium]] in 31 BC. In 27 BC the [[Roman Senate|Senate]] made Octavian ''[[princeps]]'' ("first citizen") with [[proconsul]]ar ''[[imperium]]'', thus beginning the [[Principate]] (the first epoch of Roman imperial history, usually dated from 27 BC to 284 AD), and gave him the title ''[[Augustus (title)|Augustus]]'' ("the venerated"). Although the republic stood in name, Augustus had all meaningful authority.<ref>{{Cite book |last=Syme |first=Ronald |title=The Roman Revolution |date=1939 |publisher=Oxford University Press |pages=3–4 |author-link=Ronald Syme}}</ref> Since his rule began an unprecedented period of peace and prosperity, he was so loved that he came to hold the power of a monarch ''[[de facto]]'' if not ''[[de jure]]''. During the years of his rule, a new constitutional order emerged (in part organically and in part by design), so that, upon his death, this new constitutional order operated as before when [[Tiberius]] was accepted as the new emperor.{{Citation needed|date=February 2024}}