Roman Military History and Reforms

Home | Category: Military


Samnite War

On the following document, the American historian William Stearns Davis wrote: “Among the very old formulas and usages that survived at Rome down to relatively late times, this method of declaring war holds a notable place. It was highly needful to observe all the necessary formalities in beginning hostilities, otherwise the angry gods would turn their favor to the enemy. Ancus Marcius, the fourth king of Rome, was at once a man of peace and an efficient soldier; and on the outbreak of a war with the Latins he is said to have instituted the customs which later ages of Romans observed in war.”

On the Roman Way of Declaring War around 650 B.C., the Roman historian Livy (59 B.C.- A.D. 17 ) Wrote in “History of Rome” I. 32: “Inasmuch as Numa had instituted the religious rites for days of peace, Ancus Marcius desired that the ceremonies relating to war might be transmitted by himself to future ages. Accordingly he borrowed from an ancient folk, the Aequicolae, the form which the [Roman] heralds still observe, when they make public demand for restitution. The [Roman] envoy when he comes to the frontier of the offending nation, covers his head with a woolen fillet, and says: Hear, O Jupiter, and hear ye lands _____ [i.e., of such and such a nation], let Justice hear! I am a public messenger of the Roman people. Justly and religiously I come, and let my words bear credit! Then he makes his demands, and follows with a solemn appeal to Jupiter. If I demand unjustly and impiously that these men and goods [in question] be given to me, the herald of the Roman people, then suffer me never to enjoy again my native country! [Source: William Stearns Davis, ed., “Readings in Ancient History: Illustrative Extracts from the Sources,” 2 Vols. (Boston: Allyn and Bacon, 1912-13), Vol. II: Rome and the West, pp. 7-9.

“These words he repeats when he crosses the frontiers; he says them also to the first man he meets [on the way]; again when he passes the gate; again on entering the [foreigners'] market-place, some few words in the formula being changed. If the persons he demands are not surrendered after thirty days, he declares war, thus: Hear, O Jupiter and you too, Juno — Romulus also, and all the celestial, terrestrial, and infernal gods! Give us ear! I call you to witness that this nation _____ is unjust, and has acted contrary to right. And as for us, we will consult thereon with our elders in our homeland, as to how we may obtain our rights.

“After that the envoy returns to Rome to report, and the king was wont at once to consult with the Senators in some such words as these, Concerning such quarrels as to which the pater patratus [i.e., the head of the Roman heralds] of the Roman people has conferred with the pater patratus of the ____ people, and with that people themselves, touching what they ought to have surrendered or done and which things they have not surrendered nor done [as they ought]; speak forth, he said to the senator first questioned, what think you? Then the other said, I think that [our rights] should be demanded by a just and properly declared war, and for that I give my consent and vote. Next the others were asked in order, and when the majority of those present had reached an agreement, the war was resolved upon.

“It was customary for the fetialis to carry in his hand a javelin pointed with steel, or burnt at the end and dipped in blood. This he took to the confines of the enemy's country, and in the presence of at least three persons of adult years, he spoke thus: Forasmuch as the state of the __ has offended against the Roman People, the Quirites; and forasmuch as the Roman People the Quirites have ordered that there should be war with and the Senate of the Roman People has duly voted that war should be made upon the enemy ___ : I, acting for the Roman People, declare and make actual war upon the enemy!

“So saying he flung the spear within the hostile confines. After this manner restitution was at that time demanded from the Latins [by Ancus Marcius] and war proclaimed; and the usage then established was adopted by posterity.”

Websites on Ancient Rome: Internet Ancient History Sourcebook: Rome ; Internet Ancient History Sourcebook: Late Antiquity ; Forum Romanum ; “Outlines of Roman History”; “The Private Life of the Romans”|; BBC Ancient Rome; Perseus Project - Tufts University; ; Lacus Curtius; The Roman Empire in the 1st Century; The Internet Classics Archive ; Bryn Mawr Classical Review; De Imperatoribus Romanis: An Online Encyclopedia of Roman Emperors; British Museum; Oxford Classical Art Research Center: The Beazley Archive ; Metropolitan Museum of Art; The Internet Classics Archive ; Cambridge Classics External Gateway to Humanities Resources; Internet Encyclopedia of Philosophy; Stanford Encyclopedia of Philosophy; Ancient Rome resources for students from the Courtenay Middle School Library ; History of ancient Rome OpenCourseWare from the University of Notre Dame / ; United Nations of Roma Victrix (UNRV) History

Marius Reforms of the Roman Military

Triumph of Marius

Gaius Marius (157 - 86 B.C.) reorganized the Roman army so that it was no longer a raw body of citizens arranged according to wealth; but a trained body of soldiers drawn from all classes of society, and devoted to their commander.

Dr Jon Coulston of the University of St. Andrews wrote for the BBC: Marius “is credited with a number of reforms responsible for formalising trends which had long been developing in the recruitment and organisation of the Roman army. Under Marius, property qualifications for recruitment were relaxed, accelerating the army's evolution from a militia to a professional force of soldiers dependent on the state for equipment and pay. [Source: Dr Jon Coulston, BBC, February 17, 2011 |::|]

“At the same time, Jupiter's eagle became the prime standard of each legion, contributing to the development of these formations as standing institutions. Internally, the legion came increasingly to rely upon the cohort of 480 men, rather than the maniple of paired 'centuries' - a 'maniple' being 120 men. (The cohort continued to be orgainsed as six centuries in three pairs and the titles of their centurions continued in use for hundreds of years.) This battalion-sized formation was much more tactically resilient in the field against western barbarian warbands and eastern cavalry armies the Romans faced during the later republic. |::|

Military and Army Reorganization Under Augustus

While Augustus knew that his power must have some military support, he was careful not to make the army a burden to the people. He therefore reduced the number of legions from fifty to twenty-five. As each legion contained not more than six thousand men, the whole army did not exceed one hundred and fifty thousand soldiers. These legions were distributed through the frontier provinces; the inner provinces and Italy were thus not burdened by the quartering of troops. To support the imperial authority at home, and to maintain public order, Augustus organized a body of nine thousand men called the “praetorian guard,” which force was stationed at different points outside of Rome. [Source: “Outlines of Roman History” by William C. Morey, Ph.D., D.C.L. New York, American Book Company (1901), \~]

Dr Jon Coulston of the University of St. Andrews wrote for the BBC: “Augustus (ruled 31 B.C. - 14 AD) was able to establish the Roman army on a permanent, financially manageable footing. The number of legions was reduced from 60 to 28 (then down to 25 in 9 AD), and numerous colonies were established in Italy, in the more Romanised provinces and in areas which required tight control. Colonies became an important source of future citizen recruitment. [Source: Dr Jon Coulston, BBC, February 17, 2011 |::|]

“Legions were grouped initially in regions which were not fully subdued, such as Spain and the Balkans. But in the longer term they were poised for future expansion, as in Germany and Syria. Alongside the legions there were non-citizen regiments, permanently established on the model of legionary cohorts for infantry, and similar sized units (alae) for cavalry. |Collectively known as auxilia, these units exploited the regional military traditions of the empire and its fringes to supply cavalry, archers, and light troops. They were commanded by equestrian officers - more politically reliable than the senators whose social standing was necessary for commanding citizen troops. Senators governed provinces and commanded legions, but Augustus was careful to limit their terms in office and to fill sensitive posts with equestrians, such as command of the newly formalised Praetorian Guard. |::|

Suetonius wrote: “Of his military forces he assigned the legions and auxiliaries to the various provinces, stationed a fleet at Misenum and another at Ravenna, to defend the Upper and Lower seas, and employed the remainder partly in the defence of the city and partly in that of his own person, disbanding a troop of Calagurritani which had formed a part of his body-guard until the overthrow of Antonius, and also one of Germans, which he had retained until the defeat of Varus. However, he never allowed more than three cohorts to remain in thc city and even those were without a permanent camp; the rest he regularly sent to winter or summer quarters in the towns near Rome.. [Source: Suetonius (c.69-after 122 A.D.): “De Vita Caesarum — Divus Augustus” (“The Lives of the Caesars — The Deified Augustus”), written A.D. c. 110, “Suetonius, De Vita Caesarum,” 2 Vols., trans. J. C. Rolfe (Cambridge, Mass.: Harvard University Press, 1920), pp. 123-287]

“After the civil wars he never called any of the troops "comrades," either in the assembly or in an edict, but always "soldiers"; and he would not allow them to be addressed otherwise, even by those of his sons or stepsons who held military commands, thinking the former term too flattering for the requirements of discipline, the peaceful state of the times, and his own dignity and that of his household. Except as a fire-brigade at Rome, and when there was fear of riots in times of scarcity, he employed freedmen as soldiers only twice: once as a guard for the colonies in the vicinity of Illyricum, and again to defend the bank of the river Rhine; even these he levied, when they were slaves, from men and women of means and at once gave them freedom; and he kept them under their original standard [i.e., he kept them apart from the rest in the companies in which they were first enrolled], not mingling them with the soldiers of free birth or arming them in the same fashion

As military prizes he was somewhat more ready to give trappings [the phalerae wre discs or plates of metal attached to a belt or to the harness of horses] or collars, valuable for their gold and silver, than crowns for scaling ramparts or walls, which conferred high honour; the latter he gave as sparingly as possible and without favouritism, often even to the common soldiers. He presented Marcus Agrippa with a blue banner in Sicily after his naval victory. Those vho had celebrated triumphs were the only ones whom he thought ineligible for prizes, even though they had been the companions of his campaigns and shared in his victories, on the ground that they themselves had the privilege of bestowing such honours wherever they wished. He thought nothing less becoming in a well-trained leader than haste and rashness, and, accordingly, favourite sayings of his were: "More haste, less speed"; "Better a safe commander than a bold"; and "That is done quickly enough which is done well enough." He used to say that a war or a battle should not be begun under any circumstances, unless the hope of gain was clearly greater than the fear of loss; for he likened such as grasped at slight gains with no slight risk to those who fished with a golden hook, the loss of which, if it were carried off, could not be made good by any catch.

“In passports, dispatches, and private letters he used as his seal at first a sphinx, later an image of Alexander the Great, and finally his own, carved by the hand of Dioscurides; and this his successors continued to use as their seal. He always attached to all letters the exact hour, not only of the day, but even of the night, to indicate precisely when they were written.

Military Reforms by Augustus

Suetonius wrote: “He made many changes and innovations in the army, besides reviving some usages of former times. He exacted the strictest discipline. It was with great reluctance that he allowed even his generals to visit their wives, and then only in the winter season. He sold a Roman knight and his property at public auction, because he had cut off the thumbs of two young sons, to make them unfit for military service; but when he saw that some tax gatherers were intent upon buying him, he knocked him down to a freeman of his own, with the understanding that he should be banished to the country districts, but allowed to live in freedom. [Source: Suetonius (c.69-after 122 A.D.): “De Vita Caesarum — Divus Augustus” (“The Lives of the Caesars — The Deified Augustus”), written A.D. c. 110, “Suetonius, De Vita Caesarum,” 2 Vols., trans. J. C. Rolfe (Cambridge, Mass.: Harvard University Press, 1920), pp. 123-287]

“He dismissed the entire tenth legion in disgrace, because they were insubordinate, and others, too, that demanded their discharge in an insolent fashion, he disbanded without the rewards which would have been due for faithful service. If any cohorts gave way in battle, he decimated them [i.e., executed every tenth man, selected by lot], and fed the rest on barley [instead of the usual rations of wheat]. When centurions left their posts he punished them with death, just as he did the rank and file; for faults of other kinds he imposed various ignominious penalties, such as ordering them to stand all day long before the general's tent, sometimes in their tunics without their sword-belts, or again holding ten-foot poles or even a clod of earth [carrying the pole to measure off the camp, or clods for building the rampart, was the work of the common soldiers; hence degrading for officers].

“Furthermore, he restricted all the soldiery everywhere to a fixed scale of pay and allowances, designating the duration of their service and the rewards on its completion according to each man's rank, in order to keep them from being tempted to revolution after their discharge either by age or poverty. To have funds ready at all times without difficulty for maintaining the soldiers and paying the rewards due to them, he established a military treasury, supported by new taxes. To enable what was going on in each of the provinces to be reported and known more speedily and promptly, he at first stationed young men at short intervals along the military roads, and afterwards post-chaises. The latter has seemed the more convenient arrangement, since the same men who bring the dispatches from any place can, if occasion demands, be questioned as well.

Reforms of Septimius Severus and Caracalla

Septimius Severus

Dr Jon Coulston of the University of the University of St. Andrews wrote for the BBC: “The emperor Septimius Severus (ruled 193 - 211 AD) became emperor after victory in a civil war, and his reforms were principally designed to strengthen the ruling dynasty's position. He cashiered the old 'Italian' Praetorian Guard, replacing it with men recruited from the Danubian legions which first acclaimed him emperor. He further controlled the city of Rome by stationing a newly-raised legion nearby at Albano. |::| “Severus personally led the armies of his defeated rivals against the empire's external enemies in Syria and Britain. As new provinces were established, so were new legions. Large provincial commands with three legions were divided so as to break up legionary concentrations. Military service was made more attractive by raised pay and an end to the ban on soldiers' marrying. |::|

“Severus' son and heir, Caracalla (ruled 198 - 217 AD), further raised pay and extended citizenship in 212 A.D. to all free (non-slave) members of the empire's population, thus making them eligible to pay certain citizen taxes, and thereby strengthening the army's financial base. |::|

Soldier-Emperors and Military Anarchy (A.D. 235-284)

A 50 year period of violence and chaos began in A.D. 235 when military leaders in the provinces killed Emperor Severis Alexander and replaced him with the military strongman Maximus. Most of the leaders during this time — known variously as the period of the Military Anarchy, the Imperial Crisis, or the Soldier-Emperors — tried to keep the Roman Empire together by force and spent more time in military camps than meeting rooms and had more extensive training in violence than statesmanship. The Roman Empire at this time was coming under pressure from competing empires and hostile tribes that occupied the land just outside the empire's borders. Rome's 30 or more legions fought almost constantly to defend the empire's borders. The Germans on the Rhine and the Goths on the Danube were particularly fierce and aggressive.

In the midst of these external perils, the Roman Empire was threatened on the inside by the appearance of usurpers in every part of the empire—in Asia, in Egypt, in Greece, in Illyricum, and in Gaul. This is called the time of the “thirty tyrants”; although Gibbon counts only nineteen of these so-called tyrants during the reign of Gallienus. If we should imagine another calamity in addition to those already mentioned, it would be famine and pestilence—and from these, too, Rome now suffered. From the reign of Decius to the reign of Gallienus, a period of about fifteen years, the empire was the victim of a furious plague, which is said to have raged in every province, in every city, and almost in every family. With invasions from without and revolts and pestilence within, Rome never before seemed so near to destruction. [Source: “Outlines of Roman History” by William C. Morey, Ph.D., D.C.L. New York, American Book Company (1901), \~]


According to the Metropolitan Museum of Art: “In the age of the soldier-emperors, between the assassination of Alexander Severus, the last of the Severans, in 235 A.D. and the beginning of Diocletian's reign in 284, at least sixteen men bore the title of emperor. Most were fierce military men and none could hold the reins of power without the support of the army. Almost all, having taken power upon the murder of the preceding emperor, came to a premature and violent end. Social life declined in Roman towns and instead flourished among the country aristocracy, whose secure lifestyle in large fortified estates foreshadowed medieval feudalism.\^/ [Source: Department of Greek and Roman Art, The Severan Dynasty (193–235)", The Metropolitan Museum of Art, October 2000,]

Dr Jon Coulston of the University of St. Andrews wrote for the BBC: “Third century emperors relied on the army for their position more than on any other element of Roman society. This made them especially vulnerable to usurpation by successful regional generals. The rise of new external enemies, such as the Goths and the Sassanid Persians, exacerbated the problem by creating multiple crises on different frontiers. For significant periods, usurpers based at Trier in Germany and Palmyra in Syria hived off groups of provinces as independent 'empires'. [Source: Dr Jon Coulston, BBC, February 17, 2011 |::|]

Pat Southern wrote for the BBC: “Under pressure on two frontiers, the Romans started to squabble among themselves. Civilians distrusted their own armies and the soldiers distrusted some of their commanders - even the emperor to whom they had sworn allegiance. So they proclaimed new emperors. The army had always been able to make or break emperors, but never in such quick succession as they did now. After the assassination of Severus Alexander in 235 AD, the soldiers in various parts of the empire proclaimed fifty emperors in about the same number of years. “Some of these emperors survived for only a few months, despatched by rival armies or even by the troops who had recently proclaimed them. To be declared emperor once marked the apogee of a man's career. In the third century it was a death sentence. [Source: Pat Southern, BBC, February 17, 2011 |::|]

Diocletian's Military Reforms

Camp of Diocletian in Palmyra, Syria

Ralph W. Mathisen of the University of South Carolina wrote: “As emperor, Diocletian was faced with many problems. His most immediate concerns were to bring the mutinous and increasingly barbarized Roman armies back under control and to make the frontiers once again secure from invasion. His long-term goals were to restore effective government and economic prosperity to the empire. Diocletian concluded that stern measures were necessary if these problems were to be solved. He felt that it was the responsibility of the imperial government to take whatever steps were necessary, no matter how harsh or innovative, to bring the empire back under control. [Source: Ralph W. Mathisen, University of South Carolina ^|^]

“Diocletian was able to bring the army back under control by making several changes. He subdivided the roughly fifty existing provinces into approximately one hundred. The provinces also were apportioned among twelve "dioceses," each under a "vicar," and later also among four "prefectures," each under a "praetorian prefect." As a result, the imperial bureaucracy became increasingly bloated. He institutionalized the policy of separating civil and military careers. He divided the army itself into so-called "border troops," actually an ineffective citizen militia, and "palace troops," the real field army, which often was led by the emperor in person. ^|^ “Once the army was under control, Diocletian could turn his attention to other problems. The borders were restored and strengthened. In the early years of his reign, Diocletian and his subordinates were able to defeat foreign enemies such as Alamanni, Sarmatians, Saracens, Franks, and Persians, and to put down rebellions in Britain and Egypt. The easter frontier was actually expanded. ^|^

Constantine Reorganizes the Roman Military

Constantine also re-organized the military. One of the chief defects of the early empire was the improper position which the army occupied in the state. This defect is seen in two ways. In the first place, the army was not subordinate to the civil authority. During the period of Military Anarchy and earlier the elite praetorian guards acted like kingmakers resulting in a military despotism. In the second place, the military power was not separated from the civil power. In the early empire, every governor of a province had not only civil authority, but he also had command of an army, so that he could resist the central government if he were so disposed. But Constantine changed all this. He abolished the Roman garrison or praetorian guard. He gave to the territorial governors only a civil authority; and the whole army was organized under distinct officers, and made completely subject to the central power of the empire. This change tended to prevent, on the one hand, a military despotism; and, on the other hand, the revolt of local governors. [Source: “Outlines of Roman History” by William C. Morey, Ph.D., D.C.L. New York, American Book Company (1901), \~]


Dr Jon Coulston of the University of St. Andrews wrote for the BBC: Constantine’s “power-base was the highest calibre army close to Italy, that of the north-western provinces. This already recruited heavily from the barbarians across the Rhine in non-Roman Germany. New infantry regiments were formed alongside new cavalry formations, and both were closely attached to the emperor's entourage (comitatus). They became distinct from more static troops on the frontiers, both in status and strategic mobility. [Source: Dr Jon Coulston, BBC, February 17, 2011 |::|]

“These entourage armies grew in size over the fourth century A.D. and had to be centrally supplied from state workshops. They were supposedly loyal, directly under the emperor's eye and formed a mobile reserve which could address military crises by moving quickly from region to region. Periodically, frontier units could be promoted to the higher status of comitatenses, and disloyal regiments could be punished with re-assignment to frontier (limes) duties with the lower tier limitanei. These trends of political centralisation but increased mobility can be traced through the reforms of Severus, Gallienus and Diocletian.” |::|

Stilicho and the Rise of the Foederati

Jon Coulston of the University of St. Andrews wrote for the BBC: “During the fourth century, Germany across the Rhine and Upper Danube became a prime source of army recruitment, notably to the elite units of the emperor's comitatus. However, huge losses sustained in the late fourth century, notably at the Battle of Hadrianopolis (378 AD), forced the eastern government of the emperor Theodosius (ruled 379 - 395 AD) and his successors to rely increasingly on barbarian warbands brought wholesale and still under the command of their native leaders into the Roman army. [Source: Dr Jon Coulston, BBC, February 17, 2011 |::|]

“This is reflected archaeologically across the northern provinces by the occurrence of cemeteries containing a barbarian rite of burial with military equipment, the latter being manufactured and supplied by the Roman state. In the fifth century, some of the Germanic war leaders became so dominant that emperors bestowed the highest titles on them and left military command almost entirely in their hands. |::|

“One such leader was the Vandal general Stilicho, who effectively ruled the western Roman empire (395 - 408 AD) on behalf of Theodosius's son, Honorius. He fought off the Goth Alaric, but lost influence when other barbarians overran the Rhine and Danube provinces. After Stilicho was executed, Honorius was powerless against Alaric who sacked Rome in 410 AD. |::|

Image Sources: Wikimedia Commons

Text Sources: Internet Ancient History Sourcebook: Rome ; Internet Ancient History Sourcebook: Late Antiquity ; Forum Romanum ; “Outlines of Roman History” by William C. Morey, Ph.D., D.C.L. New York, American Book Company (1901), \~\; “The Private Life of the Romans” by Harold Whetstone Johnston, Revised by Mary Johnston, Scott, Foresman and Company (1903, 1932) |+|; BBC Ancient Rome ; Perseus Project - Tufts University; ; MIT, Online Library of Liberty, ; Metropolitan Museum of Art, National Geographic, Smithsonian magazine, New York Times, Washington Post, Los Angeles Times, Live Science, Discover magazine, Times of London, Natural History magazine, Archaeology magazine, The New Yorker, Encyclopædia Britannica, "The Discoverers" [∞] and "The Creators" [μ]" by Daniel Boorstin. "Greek and Roman Life" by Ian Jenkins from the British Museum.Time, Newsweek, Wikipedia, Reuters, Associated Press, The Guardian and various books and other publications.

Last updated October 2018

This site contains copyrighted material the use of which has not always been authorized by the copyright owner. Such material is made available in an effort to advance understanding of country or topic discussed in the article. This constitutes 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. If you are the copyright owner and would like this content removed from, please contact me.