Ancient Rome

=== Military ===
{{Main|Military history of ancient Rome|Military of ancient Rome|Structural history of the Roman military|Roman army|Roman navy}}
{{Ancient Rome military sidebar}}
[[File:Altar Domitius Ahenobarbus Louvre n3bis.jpg|thumb|[[Altar of Domitius Ahenobarbus]], c.&nbsp;122 BC; the altar shows two Roman infantrymen equipped with long ''[[Scutum (shield)|scuta]]'' and a cavalryman with his horse. All are shown wearing [[chain mail]] armour.]]
[[File:Römerturm, Auf dem Gaulskopf.jpg|thumb|upright|Roman [[tower]] ([[Reconstruction (architecture)|reconstruction]]) at [[Upper Germanic-Rhaetian Limes|Limes]] – [[Taunus]] / Germany]]
The early [[Roman army]] ({{Circa|500&nbsp;BC}}) was, like those of other contemporary [[city-state]]s influenced by Greek civilisation, a citizen ''[[militia]]'' that practised [[hoplite]] tactics. It was small and organised in five classes (in parallel to the ''[[Roman assemblies|comitia centuriata]]'', the body of citizens organised politically), with three providing hoplites and two providing light infantry. The early Roman army was tactically limited and its stance during this period was essentially defensive.{{Sfn|Keegan|1993|pages=[https://archive.org/details/historyofwarfare00keeg/page/263 263–264]}}<ref name="potter">{{Cite book |last=Potter |first=David |title=The Roman Army and Navy |date=2004 |pages=[https://archive.org/details/cambridgecompani0000unse_s0h2/page/67 67–70]}} in {{Harvnb|Flower|2004}}</ref><ref>For a discussion of hoplite tactics and their sociocultural setting, see {{Cite book |first=Victor Davis |last=Hanson |title=The Western Way of War: Infantry Battle in Classical Greece |publisher=Alfred A. Knopf |location=New York |date=1989 |isbn=0394571886}}</ref>

By the 3rd century BC, the Romans abandoned the hoplite formation in favour of a more flexible system in which smaller groups of 120 (or sometimes 60) men called ''[[Maniple (military unit)|maniples]]'' could manoeuvre more independently on the battlefield. Thirty maniples arranged in three lines with supporting troops constituted a [[Roman legion|legion]], totalling between 4,000 and 5,000 men.{{Sfn|Keegan|1993|pages=[https://archive.org/details/historyofwarfare00keeg/page/263 263–264]}}<ref name= potter/> The early Republican legion consisted of five sections: the three lines of manipular heavy infantry (''[[hastati]]'', ''[[principes]]'' and ''[[triarii]])'', a force of light infantry (''[[velites]]''), and the cavalry (''[[equites]]''). With the new organisation came a new orientation toward the offensive and a much more aggressive posture toward adjoining city-states.{{Sfn|Keegan|1993|pages=[https://archive.org/details/historyofwarfare00keeg/page/263 263–264]}}<ref name= potter/> At nominal full strength, an early Republican legion included 3,600 to 4,800 heavy infantry, several hundred light infantry, and several hundred cavalrymen.{{Sfn|Keegan|1993|pages=[https://archive.org/details/historyofwarfare00keeg/page/263 263–264]}}{{Sfn|Goldsworthy|1996|p=33}}<ref>{{Cite book |editor-first=Jo-Ann |editor-last=Shelton |title=As the Romans Did: A Sourcebook in Roman Social History |publisher=Oxford University Press |location=New York |date=1998 |isbn=019508974X |pages=245–249}}</ref>

Until the late Republican period, the typical legionary was a property-owning citizen farmer from a rural area (an ''adsiduus'') who served for particular (often annual) campaigns,{{Efn|Between 343 BC and 241 BC, the Roman army fought in every year but five.<ref>{{Cite book |last=Oakley |first=Stephen P. |title= The Early Republic |date=2004 |page=[https://archive.org/details/cambridgecompani0000unse_s0h2/page/27 27]}} in {{Harvnb|Flower|2004}}</ref>}} and who supplied his own equipment. After 200&nbsp;BC, economic conditions in rural areas deteriorated as manpower needs increased, so that the property qualifications for compulsory service were gradually reduced. Beginning in the 3rd century BC, legionaries were paid a [[stipend]] (''stipendium''). By the time of Augustus, the ideal of the citizen-soldier had been abandoned and the legions had become fully professional. At the end of the [[Final War of the Roman Republic|Civil War]], Augustus reorganised Roman military forces, discharging soldiers and disbanding legions. He retained 28 legions, distributed through the provinces of the Empire.<ref>{{Harvnb|Mackay|2004|pp=249–250}} Mackay points out that the number of legions grew to 30 by 125 AD and 33 during the [[Severan dynasty|Severan]] period (200–235 AD).</ref>

During the [[Principate]], the tactical organisation of the Army continued to evolve. The {{lang|la|auxilia}} remained independent cohorts, and legionary troops often operated as groups of cohorts rather than as full legions. A new and versatile type of unit, the ''cohortes equitatae'', combined cavalry and legionaries in a single formation. They could be stationed at garrisons or outposts and could fight on their own as balanced small forces or combine with similar units as a larger, legion-sized force. This increase in organizational flexibility helped ensure the long-term success of Roman military forces.{{Sfn|Goldsworthy|1996|pp=36–37}} The Emperor [[Gallienus]] (253–268&nbsp;AD) began a reorganisation that created the last military structure of the late Empire. Withdrawing some legionaries from the fixed bases on the border, Gallienus created mobile forces (the ''[[comitatenses]]'' or field armies) and stationed them behind and at some distance from the borders as a strategic reserve. The border troops (''[[limitanei]]'') stationed at fixed bases continued to be the first line of defence. The basic units of the field army were regimental; ''legiones'' or {{lang|la|auxilia}} for infantry and ''[[vexillation]]es'' for cavalry. Nominal strengths may have been 1,200 men for infantry regiments and 600 for cavalry, but actual troop levels could have been much lower—800 infantry and 400 cavalry.{{Sfn|Elton|1996|pages=89–96}} Many infantry and cavalry regiments operated in pairs under the command of a ''[[comes]]''. Field armies included regiments recruited from allied tribes and known as ''[[foederati]]''. By 400&nbsp;AD, ''foederati'' regiments had become permanently established units of the Roman army, paid and equipped by the Empire, led by a Roman tribune and used just as Roman units were used. The Empire also used groups of barbarians to fight along with the legions as allies without integration into the field armies, under overall command of a Roman general, but led by their own officers.{{Sfn|Elton|1996|pages=89–96}}

Military leadership evolved over the course of the history of Rome. Under the monarchy, the hoplite armies were led by the kings. During the early and middle Roman Republic, military forces were under the command of one of the two elected [[Roman consul|consuls]] for the year. During the later Republic, members of the Roman Senatorial elite, as part of the normal sequence of elected public offices known as the ''[[cursus honorum]]'', would have served first as ''[[quaestor]]'' (often posted as deputies to field commanders), then as ''[[praetor]]''.<ref name="bcorrey">{{Cite book |last=Brennan |first=Correy T. |title=Power and Process Under the Republican 'Constitution' |date=2004 |pages=[https://archive.org/details/cambridgecompani0000unse_s0h2/page/66 66–68]}} in {{Harvnb|Flower|2004}}
</ref>{{Sfn|Goldsworthy|1996|pp=121–125}} Following the end of a term as praetor or consul, a Senator might be appointed by the Senate as a [[Promagistrate|''propraetor'']] or [[Promagistrate|''proconsul'']] (depending on the highest office held before) to govern a foreign province. Under Augustus, whose most important political priority was to place the military under a permanent and unitary command, the Emperor was the legal commander of each legion but exercised that command through a ''[[legatus]]'' (legate) he appointed from the Senatorial elite. In a province with a single legion, the legate commanded the legion (''[[legatus legionis]]'') and served as provincial governor, while in a province with more than one legion, each legion was commanded by a legate and the legates were commanded by the provincial governor (also a legate but of higher rank).{{Sfn|Mackay|2004|pp=245–252}}

During the later stages of the Imperial period (beginning perhaps with [[Diocletian]]), the Augustan model was abandoned. Provincial governors were stripped of military authority, and command of the armies in a group of provinces was given to generals ([[Dux|''duces'']]) appointed by the Emperor. These were no longer members of the Roman elite but men who came up through the ranks and had seen much practical soldiering. With increasing frequency, these men attempted (sometimes successfully) to usurp the positions of the Emperors. Decreased resources, increasing political chaos and civil war eventually left the Western Empire vulnerable to attack and takeover by neighbouring barbarian peoples.<ref>{{Harvnb|Mackay|2004|pp=295–296}} Also chapters 23–24.</ref>

====Roman navy====
[[File:D473-birème romaine-Liv2-ch10.png|thumb|A Roman naval [[bireme]] depicted in a relief from the [[Temple of Fortuna Primigenia]] in [[Praeneste]] ([[Palestrina|Palastrina]]),

<ref>{{Cite book |first=D.B. |last=Saddington |editor-first=Paul |editor-last=Erdkamp |date=2011 |orig-date=2007 |title=A Companion to the Roman Army |chapter=Classes: the Evolution of the Roman Imperial Fleets |pages=201–217 (Plate 12.2 on p. 204) |publisher=Wiley-Blackwell |isbn=978-1405121538}}</ref>

 which was built {{Circa|120 BC}};<ref>Coarelli, Filippo (1987), ''I Santuari del Lazio in età repubblicana''. NIS, Rome, pp. 35–84.</ref> exhibited in the Pius-Clementine Museum ([[Museo Pio-Clementino]]) in the [[Vatican Museums]].]]

Less is known about the [[Roman navy]] than the Roman army. Prior to the middle of the 3rd century BC, officials known as ''duumviri navales'' commanded a fleet of twenty ships used mainly to control piracy. This fleet was given up in 278&nbsp;AD and replaced by allied forces. The [[Punic Wars|First Punic War]] required that Rome build large fleets, and it did so largely with the assistance of and financing from allies. This reliance on allies continued to the end of the Roman Republic. The [[quinquereme]] was the main warship on both sides of the Punic Wars and remained the mainstay of Roman naval forces until replaced by the time of Caesar Augustus by lighter and more manoeuvrable vessels.<ref name="Potter pp. 76-78">This paragraph is based upon Potter, pp. 76–78.</ref>

As compared with a [[trireme]], the quinquereme permitted the use of a mix of experienced and inexperienced crewmen (an advantage for a primarily land-based power), and its lesser manoeuvrability permitted the Romans to adopt and perfect [[Corvus (weapon)|boarding tactics]] using a troop of about 40 marines in lieu of the [[Naval tactics in the Age of Galleys|ram]]. Ships were commanded by a ''[[navarch]]'', a rank equal to a centurion, who was usually not a citizen. Potter suggests that because the fleet was dominated by non-Romans, the navy was considered non-Roman and allowed to atrophy in times of peace.<ref name="Potter pp. 76-78"/>

Information suggests that by the time of the late Empire (350&nbsp;AD), the Roman navy comprised several fleets including warships and merchant vessels for transportation and supply. Warships were oared sailing galleys with three to five banks of oarsmen. Fleet bases included such ports as Ravenna, Arles, Aquilea, Misenum and the mouth of the Somme River in the West and Alexandria and Rhodes in the East. Flotillas of small river craft (''classes'') were part of the ''limitanei'' (border troops) during this period, based at fortified river harbours along the Rhine and the Danube. That prominent generals commanded both armies and fleets suggests that naval forces were treated as auxiliaries to the army and not as an independent service. The details of command structure and fleet strengths during this period are not well known, although fleets were commanded by prefects.{{Sfn|Elton|1996|pages=99–101}}