De Re Militari De Re Militari ( Latin " Concerning Military Matters " ) , also Epitoma Rei Militaris , is a treatise by the late Latin writer Publius Flavius Vegetius Renatus about Roman warfare and military principles as a presentation of methods and practices in use during the height of Rome ' s power , and responsible for that power . The extant text dates to the 5th century . Vegetius emphasized things such as training of soldiers as a disciplined force , orderly strategy , maintenance of supply lines and logistics , quality leadership and use of tactics and even deceit to ensure advantage over the opposition . He was concerned about selection of good soldiers and recommended hard training of at least four months before the soldier was accepted into the ranks . The leader of the army ( " dux " or duke ) had to take care of the men under his command and keep himself informed about the movements of the enemy to gain advantage in the battle . " De Re Militari " became a military guide in the Middle Ages . Even after the introduction of gunpowder to Europe , it was carried by general officers and their staffs as a field guide to methods . Friends and subordinates customarily presented embellished copies as gifts to leaders . It went on into the 18th and 19th centuries as a source of policy and strategy to the major states of Europe . In that sense " De Re Militari " is a projection of Roman civilization into modern times and a continuation of its influence on its cultural descendants . Authorship and composition . The author of " De Re Militari " was Publius Flavius Vegetius Renatus , who lived in the late 4th century and possibly the early 5th century . The name of the work has a number of variants , including " Epitoma Rei Militaris " , but there are other problems with accepting it at face value as the verbatim work of Vegetius . Some of the manuscripts have a note that the text was revised for the 7th time in Constantinople in the consulate of Valentinian , who must have been Valentinian III , reigning 425 - 455 . Vegetius ' dates are not known or the circumstances under which the work was revised . The year 450 is taken as the latest possible time the work could have been written , assuming he did all seven revisions in just a few years . The initial date of the window is established by Vegetius ' own statement that he wrote covering the time " usque ad tempus divi Gratiani " , " up to the time of the divine Gratian . " As emperors did not become gods generally until they died , the statement sets the initial possible date ( " terminus post quem " ) at 383 , the year Gratian died . If the earlier date is preferred , it is unlikely Vegetius did all seven revisions or even one of them . There is no reason to question his general authorship , however . The work is dedicated to a mysterious emperor , whose identity is unknown but whom Vegetius must have assumed to have been known to his intended readership . It may be that he wrote on behalf of military reform under the patronage of Theodosius I . In that case he would have been alive in the window 378 - 395 , the dates of Theodosius ' reign . This article adopts that point of view and assigns an approximate date of 390 to the work , which would not be , then , word for word the same as what Vegetius wrote , accounting for the title variants . Sources . Vegetius based his treatise on descriptions of Roman armies , especially those of the mid to late Republic . As G . R . Watson observes , Vegetius ' " Epitoma " " is the only ancient manual of Roman military institutions to have survived intact . " Despite this , Watson is dubious of its value , for he " was neither a historian nor a soldier : his work is a compilation carelessly constructed from material of all ages , a congeries of inconsistencies . " These antiquarian sources , according to his own statement , were Cato the Elder , Cornelius Celsus , Frontinus , Paternus and the imperial constitutions of Augustus , Trajan and Hadrian ( 1 . 8 ) . Contents of the treatise . Vegetius ' epitome mainly focuses on military organisation and how to react to certain occasions in war . Vegetius explains how one should fortify and organise a camp , how to train troops , how to handle undisciplined troops , how to handle a battle engagement , how to march , formation gauge , and many other useful methods of promoting organisation and valour in the legion . The treatise is carefully laid out in subsections . They are organized into four books : Book I . The first book , headed " Primus liber electionem edocet iuniorum , ex quibus locis uel quales milites probandi sint aut quibus armorum exercitiis imbuendi " , explains the selection of recruits , from which places and what kinds ( of men ) are soldiers to be authorised and with what exercises of arms they are to be indoctrinated . Vegetius also describes in detail the organisation training and equipment of the army of the early Empire . Portraying the military decadence of the Late Roman Empire , it is a plea for army reform . Book II . The second book , " Secundus liber ueteris militiae continet morem , ad quem pedestris institui possit exercitus " , contains traditional military practices with which infantry can be created . Book III . The third book , " Tertius liber omnia artium genera , quae terrestri proelio necessaria uidentur , exponit " , sets forth all types of arts that appear to be necessary for fighting on land . It contains a series of military maxims , which became influential to military learning of commanders in later medieval Europe , from William the Silent to Frederick the Great . Some of the maxims may be mentioned here as illustrating the principles of a war for limited political objectives with which he deals : Another influential concept is that of his " seven normal dispositions for battle " . Book IV . The fourth book , " Quartus liber uniuersas machinas , quibus uel obpugnantur ciuitates uel defenduntur , enumerat ; naualis quoque belli praecepta subnectit " , enumerates " all the machines with which cities are besieged or defended " ( chapters 1 - 30 ) and adds also the precepts of naval warfare ( chapters 31 - 46 ) . It contains the best description of siegecraft in the Late Roman Empire . From it , among other things , we learn details of the siege engine called the onager , which until recently was thought to have been common in medieval sieges . Vegetius is keen to stress the shortcomings of the Roman Army in his lifetime . In order to do this he eulogises the army of the early Roman Empire . In particular he stresses the high standard of the pydars and the excellence of the training and the officer corps . In reality , Vegetius probably describes an ideal rather than the reality . The Army of the early Empire was a formidable fighting force but it probably was not in its entirety quite as good as Vegetius describes . For example , he says that recruits should be 5 Roman feet 10 inches tall ( " Epitoma " 1 . 5 ) , the equivalent of 172 cm . The average height of adult male skeletons buried in Italy between 500 BCE and 500 CE was 168 cm so it would probably have been hard to meet Vegetius ' height standards . Transmission and influence . Heavily used in its own time , " De Re Militari " became a popular manual on warfare in the Middle Ages , especially between 9th and 16th centuries , even if some of the information was unsuitable to later times and circumstances . N . P . Milner observes that it was " one of the most popular Latin technical works from Antiquity , rivalling the elder Pliny ' s " Natural History " in the number of surviving copies dating from before AD 1300 . " The early English historian Bede cites Vergetius in his prose Life of St Cuthbert . The earliest extant manuscript from England to contain Vegetius ' text is Cotton Cleopatra D . I ( of the 11th , possibly late 10th century ) . " De Re Militari " came to the forefront in the late Carolingian period through Hrabanus Maurus ( d . 856 ) , who used the text for his own manual " De Procincta Romaniae Militiae " , composed for Lothair II of Lotharingia ( r . 855 - 869 ) . Vegetius ' notes about siege craft became especially obsolete when the technology advanced and gunpowder weapons such as cannon came into widespread use . Vegetius ' suggestion of a soldier ' s religious oath to God and to the realm might have influenced knightly practices . Still , because of the lack of literacy , as a guide it was probably accessible only to aristocracy , clergy and royalty . Machiavelli very likely read Vegetius and incorporated many of his ideas into his own " The Prince " . To the modern day , 226 Latin copies of the book have survived , not including translations to various other European languages . Many of them have a copious amount of personal notes on them , pointing at matters that have interested their contemporary owners . The first printed editions are ascribed to Utrecht ( 1473 ) , Cologne ( 1476 ) , Paris ( 1478 ) , Rome ( in " Veteres de re mil . scriptores " , 1487 ) , and Pisa ( 1488 ) . A German translation by Ludwig Hohenwang appeared at Ulm in 1475 . It was translated into English , French ( by Jean de Meun and others ) , Italian ( by the Florentine judge and others ) , Catalan , Spanish , Czech , and Yiddish before the invention of printing . An early English version ( via French ) was published by Caxton in 1489 . However , after the first printed editions , Vegetius ' position as the premier military authority began to decline , as ancient historians such as Polybius became available . Niccolò Machiavelli attempted to address Vegetius ' s defects in his " L ' arte della Guerra " ( Florence , 1521 ) , with heavy use of Polybius , Frontinus and Livy , but Justus Lipsius ' accusation that he confused the institutions of diverse periods of the Roman Empire and G . Stewechius ' opinion that the survival of Vegetius ' work led to the loss of his named sources were more typical of the late Renaissance . While as late as the 18th century we find so eminent a soldier as Marshal Puysegur basing his own works on this acknowledged model , and the famous Prince de Ligne wrote " " C ' est un livre d ' or " " . In Milner ' s words , Vegetius ' work suffered " a long period of deepening neglect " . Title . The work is known by a number of variant titles . Here are some titles from among the incunabula , books printed before 1501 : The common element of all the names are the two cases of " res militaris " ( nominative case ) : " rei militaris " ( genitive case ) and " re militari " ( ablative case ) . The classical form would have been the ablative . Vegetius uses " epitomata " , plural of the Greek epitoma , in his other surviving work on doctoring mules . English translations precede printed books . Manuscript 18A . Xii in the Royal Library , written and ornamented for Richard III of England , is a translation of Vegetius . It ends with a paragraph starting : " Here endeth the boke that clerkes clepethe in Latyne Vegecii de re militari . " The paragraph goes on to date the translation to 1408 . The translator is identified in Manuscript No . 30 of Magdalen College , Oxford , as John Walton , 1410 translator of Boethius . References . Editions and translations . The most reliable modern edition is that of Michael D . Reeve ( Oxford , 2004 ) . For a detailed critical estimate of Vegetius ' works and influence , see Max Jahns , " Geschiche der Kriegswissenschaften " , i . 109 - 125 .