{{Infobox Roman emperor 
| title = Emperor of the Roman Empire 
|name=Constantine I
| full name       =Flavius Valerius Aurelius Constantinus
| image           =200px
| caption         =Head of Constantine's colossal statue at the Capitoline Museums
| reign           =Augustus in the West, officially made Caesar by Severus as Augustus, by agreement with Caesar in 309)<br>29 October 312&nbsp;&ndash;&nbsp;19 September 324 (undisputed Augustus in the West, senior Augustus in the empire)<br>19 September 324&nbsp;&ndash;&nbsp;22 May 337 (emperor of united empire)
| predecessor     =Constantius Chlorus
| successor       =Constantine II, Constantius II and Constans
| spouse 1         =Minervina, died or divorced before 307
| spouse 2        =Fausta
| children           =Constantine II, Constantius II and Constans
| dynasty         =Constantinian
| father          =Constantius Chlorus
| mother          =Helena
| venerated_in    =Eastern Orthodoxy<br>Lutheranism<br>Oriental Orthodoxy<br>Roman Catholicism
| date of birth   =27 February ''ca''. 272<ref name=birthdate/>
| place of birth  =Naissus (modern Niš, Serbia) 
| date of death   =22 May 337
| place of death  = Nicomedia (modern Izmit, Turkey)
| place of burial =  
|}}
'''Flavius Valerius Aurelius Constantinus'''<ref>In (Latin Constantine's official imperial title was <small>IMPERATOR CAESAR FLAVIVS CONSTANTINVS PIVS FELIX INVICTVS AVGVSTVS</small>, ''Imperator Caesar Flavius Constantine Augustus, the pious, the fortunate, the undefeated''. After 312, he added <small>MAXIMVS</small> ("the greatest"), and after 325 replaced ("undefeated") with <small>VICTOR</small>, as ''invictus'' reminded of Western Christians), or '''Saint Constantine''' (among Eastern Orthodox and Christian Roman Emperor, Constantine reversed the persecutions of his predecessor, Diocletian, and issued (with his co-emperor Licinius) the Edict of Milan in 313, which proclaimed religious toleration throughout the empire.

The Byzantine liturgical calendar, observed by the Eastern Catholic Churches of Byzantine rite, lists both Constantine and his mother Helena as saints.  Although he is not included in the Latin Church's list of saints, which does recognize several other Constantines as saints, he is revered under the title "The Great" for his contributions to Christianity.

Constantine also transformed the ancient Greek colony of Byzantium into a new imperial residence,  Constantinople, which would remain the capital of the Byzantine Empire for over a thousand years.

==Sources==
As the Emperor who empowered Christianity throughout the Roman Empire and moved the Roman capital to the banks of the Bosphorus, Constantine was a ruler of major historical importance, but he has always been a controversial figure.<ref>Barnes, ''Constantine and Eusebius'', 272.</ref> The fluctuations in Constantine's reputation reflect the nature of the ancient sources for his reign. These are abundant and detailed,<ref>Bleckmann, "Sources for the History of Constantine" (CC), 14; Cameron, 90&ndash;91; Lenski, "Introduction" (CC), 2&ndash;3.</ref> but have been strongly influenced by the official propaganda of the period,<ref>Bleckmann, "Sources for the History of Constantine" (CC), 23&ndash;25; Cameron, 90&ndash;91; Southern, 169.</ref> and are often one-sided.<ref>Cameron, 90; Southern, 169.</ref> There are no surviving histories or biographies dealing with Constantine's life and rule.<ref>Bleckmann, "Sources for the History of Constantine" (CC), 14; Corcoran, ''Empire of the Tetrarchs'', 1; Lenski, "Introduction" (CC), 2&ndash;3.</ref> The nearest replacement is Eusebius of Caesarea's  ''Vita Constantini'', a work that is a mixture of eulogy and hagiography.<ref>Barnes, ''Constantine and Eusebius'', 265&ndash;68.</ref> Written between 335 and circa 339,<ref>Drake, "What Eusebius Knew," 21.</ref> the ''Vita'' extols Constantine's moral and religious virtues.<ref>Eusebius, ''Vita Constantini'' 1.11; Odahl, 3.</ref> The ''Vita'' creates a contentiously positive image of Constantine,<ref>Lenski, "Introduction" (CC), 5; Storch, 145&ndash;55.</ref> and modern historians have frequently challenged its reliability.<ref>Barnes, ''Constantine and Eusebius'', 265&ndash;71; Cameron, 90&ndash;92; Cameron and Hall, 4&ndash;6; Elliott, "Eusebian Frauds in the "Vita Constantini"", 162&ndash;71.</ref> The fullest secular life of Constantine is the anonymous ''Origo Constantini''.<ref>Lieu and Montserrat, 39; Odahl, 3.</ref> A work of uncertain date,<ref>Bleckmann, "Sources for the History of Constantine" (CC), 26; Lieu and Montserrat, 40; Odahl, 3.</ref> the ''Origo'' focuses on military and political events, to the neglect of cultural and religious matters.<ref>Lieu and Montserrat, 40; Odahl, 3.</ref>

Socrates, Sozomen, and Theodoret describe the ecclesiastic disputes of Constantine's later reign.<ref>Barnes, ''Constantine and Eusebius'', 225; Bleckmann, "Sources for the History of Constantine" (CC), 28&ndash;29; Odahl, 4&ndash;6.</ref> Written during the reign of Theodosius II (408&ndash;50), a century after Constantine's reign, these ecclesiastic historians obscure the events and theologies of the Constantinian period through misdirection, misrepresentation and deliberate obscurity.<ref>Barnes, ''Constantine and Eusebius'', 225; Bleckmann, "Sources for the History of Constantine" (CC), 26&ndash;29; Odahl, 5&ndash;6.</ref> The contemporary writings of the Orthodox Christian Athanasius and the ecclesiastical history of the Arian Philostorgius also survive, though their biases are no less firm.<ref>Odahl, 6, 10.</ref> 

The Córdoba,<ref>Bleckmann, "Sources for the History of Constantine" (CC), 20&ndash;21; Johnson, "Architecture of Empire" (CC), 288&ndash;91; Odahl, 11&ndash;12.</ref> epigraphic remains, and the coinage of the era complement the literary sources.<ref>Bleckmann, "Sources for the History of Constantine" (CC), 17&ndash;21; Odahl, 11&ndash;14.</ref>

==Early life==
thumb|right|Constantine's parents and siblings. Dates in square brackets indicate the possession of minor titles, such as the [[Caesar (title)|Caesar]]
Constantine, named Flavius Valerius Constantinus, was born in the 27th of February of an uncertain year,<ref>Barnes, ''Constantine and Eusebius'', 3, 39&ndash;42; Elliott, ''Christianity of Constantine'', 17; Odahl, 15; Pohlsander, "Constantine I"; Southern, 169, 341.</ref> probably near 272.<ref>Barnes, ''Constantine and Eusebius'', 3; Barnes, ''New Empire'', 39&ndash;42; Elliott, "Constantine's Conversion," 425–6; Elliott, "Eusebian Frauds," 163; Elliott, ''Christianity of Constantine'', 17; Jones, 13&ndash;14; Lenski, "Reign of Constantine" (CC), 59; Odahl, 16; Pohlsander, ''Emperor Constantine'', 14; Rodgers, 238; Wright, 495, 507.</ref> His father was Flavius Constantius, a native of Moesia Superior (later Dacia Ripensis).<ref name="CTCR">Barnes, ''Constantine and Eusebius'', 3; Lenski, "Reign of Constantine" (CC), 59&ndash;60; Odahl, 16&ndash;17.</ref> Constantius was a tolerant and politically skilled man.<ref>''Panegyrici Latini'' 8(5), 9(4); Lactantius, ''De Mortibus Persecutorum'' 8.7; Eusebius, ''Vita Constantini'' 1.13.3; Barnes, ''Constantine and Eusebius'', 13, 290.</ref> Constantine probably spent little time with his father.<ref>MacMullen, ''Constantine'', 21.</ref> Constantius was an officer in the Roman army in 272, part of the Emperor governorship of Helena, a Bithynian Greek of humble origin. It is uncertain whether she was legally married to Constantius or merely his concubine.<ref>Barnes, ''Constantine and Eusebius'', 3; Barnes, ''New Empire'', 39&ndash;40; Elliott, ''Christianity of Constantine'', 17; Lenski, "Reign of Constantine" (CC), 59, 83; Odahl, 16; Pohlsander, ''Emperor Constantine'', 14.</ref>

In July 285, Diocletian declared Gaul. Constantius left Helena to marry Maximian's stepdaughter Theodora in 288 or 289.<ref>Barnes, ''Constantine and Eusebius'', 3; Elliott, ''Christianity of Constantine'', 20; Lenski, "Reign of Constantine" (CC), 59&ndash;60; Odahl, 47, 299; Pohlsander, ''Emperor Constantine'', 14.</ref> 

Diocletian divided the Empire again in 293, appointing two Caesars (junior emperors) to rule over further subdivisions of East and West. Each would be subordinate to their respective Augustus (senior emperor) but would act with supreme authority in his assigned lands. This system would later be called the Tetrarchy. Diocletian's first appointee for the office of Caesar was Constantius; his second was Galerius, a native of Felix Romuliana (Gamzigrad, Serbia). According to Lactantius, Galerius was a brutal, animalistic man. Although he shared the paganism of Rome's aristocracy, he seemed to them an alien figure, a semi-barbarian.<ref>Lactantius, ''De Mortibus Persecutorum'' 7.1; Barnes, ''Constantine and Eusebius'', 13, 290.</ref> On March 1, Constantius was promoted to the office of Caesar, and dispatched to Gaul to fight the rebels Carausius and Allectus.<ref>Barnes, ''Constantine and Eusebius'', 3, 8; Corcoran, "Before Constantine" (CC), 40&ndash;41; Elliott, ''Christianity of Constantine'', 20; Odahl, 46&ndash;47; Pohlsander, ''Emperor Constantine'', 8&ndash;9, 14; Treadgold, 17.</ref> In spite of meritocratic overtones, the Tetrarchy retained vestiges of hereditary privilege,<ref>Barnes, ''Constantine and Eusebius'', 8&ndash;9; Corcoran, "Before Constantine" (CC), 42&ndash;43, 54.</ref> and Constantine became the prime candidate for future appointment as Caesar as soon as his father took the position. Constantine left the Balkans for the court of Diocletian, where he lived as his father's heir presumptive.<ref>Barnes, ''Constantine and Eusebius'', 3; Lenski, "Reign of Constantine" (CC), 59&ndash;60; Odahl, 56&ndash;7.</ref>

===In the East===
Constantine received a formidable education at Diocletian's court, where he learned Latin literature, Greek, and philosophy.<ref>Barnes, ''Constantine and Eusebius'', 73&ndash;74; Lenski, "Reign of Constantine" (CC), 60; Odahl, 72, 301.</ref> The cultural environment in Nicomedia was open, fluid and socially mobile, and Constantine could mix with intellectuals both pagan and Christian. He may have attended the lectures of Lactantius, a Christian scholar of Latin in the city.<ref>Barnes, ''Constantine and Eusebius'', 47, 73&ndash;74; Fowden, "Between Pagans and Christians," 175&ndash;76.</ref> Because Diocletian did not completely trust Constantius&mdash;none of the Tetrarchs fully trusted their colleagues&mdash;Constantine was held as something of a hostage, a tool to ensure Constantius' best behavior. Constantine was nonetheless a prominent member of the court: he fought for Diocletian and Galerius in Asia, and served in a variety of tribunates; he campaigned against barbarians on the Danube in 296, and fought the Persians under Diocletian in Syria (297) and under Galerius in Mesopotamia (298&ndash;99).<ref>Constantine, ''Oratio ad Sanctorum Coetum'', 16.2; Elliott, ''Christianity of Constantine'', 29&ndash;30; Lenski, "Reign of Constantine" (CC), 60; Odahl, 72&ndash;73.</ref> By late 305, he had become a tribune of the first order, a ''tribunus ordinis primi''.<ref>Elliott, ''Christianity of Constantine'', 29; Lenski, "Reign of Constantine" (CC), 61; Odahl, 72&ndash;74, 306; Pohlsander, ''Emperor Constantine'', 15. Contra: J. Moreau, ''Lactance: "De la mort des persécuteurs"'', ''Sources Chrétiennes'' 39 (1954): 313; Barnes, ''Constantine and Eusebius'', 297.</ref>

thumb|right|Head from a statue of [[Diocletian, Augustus of the East]]

Constantine had returned to Nicomedia from the eastern front by the spring of 303, in time to witness the beginnings of Diocletian's "Great Persecution", the severest persecution of Christians in Roman history.<ref>Constantine, ''Oratio ad Sanctorum Coetum'' 25; Elliott, ''Christianity of Constantine'', 30; Odahl, 73.</ref> In late 302, Diocletian and Galerius sent a messenger to the oracle of Apollo at Didyma with an inquiry about Christians.<ref>Lactantius, ''De Mortibus Persecutorum'' 10.6&ndash;11; Barnes, ''Constantine and Eusebius'', 21; Elliott, ''Christianity of Constantine'', 35&ndash;36; MacMullen, ''Constantine'', 24; Odahl, 67; Potter, 338.</ref> Constantine could recall his presence at the palace when the messenger returned, when Diocletian accepted his court's demands for universal persecution.<ref>Eusebius, ''Vita Constantini'' 2.49–52; Barnes, ''Constantine and Eusebius'', 21; Odahl, 67, 73, 304; Potter, 338.</ref> On February 23 303, Diocletian ordered the destruction of Nicomedia's new church, condemned its scriptures to the flame, and had its treasures seized. In the months that followed, churches and scriptures were destroyed, Christians were deprived of official ranks, and priests were imprisoned.<ref>Barnes, ''Constantine and Eusebius'', 22&ndash;25; MacMullen, ''Constantine'', 24&ndash;30; Odahl, 67&ndash;69; Potter, 337.</ref> 

It is unlikely that Constantine played any role in the persecution.<ref>MacMullen, ''Constantine'', 24&ndash;25.</ref> In his later writings he would attempt to present himself as an opponent of Diocletian's "sanguinary edicts" against the "worshipers of God",<ref>''Oratio ad Sanctorum Coetum'' 25; Odahl, 73.</ref> but nothing indicates that he opposed it effectively at the time.<ref>Drake, "The Impact of Constantine on Christianity" (CC), 126; Elliott, "Constantine's Conversion," 425&ndash;26.</ref> Although no contemporary Christian challenged Constantine for his inaction during the persecutions, it remained a political liability throughout his life.<ref>Drake, "The Impact of Constantine on Christianity" (CC), 126.</ref>

On Severus and Maximin were appointed, while Constantine and Maxentius were ignored.<ref>Lenski, "Reign of Constantine" (CC), 60&ndash;61; Odahl, 72&ndash;74; Pohlsander, ''Emperor Constantine'', 15.</ref>

Some of the ancient sources detail plots that Galerius made on Constantine's life in the months following Diocletian's abdication. They assert that Galerius assigned Constantine to lead an advance unit in a cavalry charge through a swamp on the middle Danube, made him enter into single combat with a lion, and attempted to kill him in hunts and wars. Constantine always emerged victorious: the lion emerged from the contest in a poorer condition than Constantine; Constantine returned to Nicomedia from the Danube with a Sarmatian captive to drop at Galerius' feet.<ref>''Origo'' 4; Lactantius, ''De Mortibus Persecutorum'' 24.3&ndash;9; Praxagoras fr. 1.2; Aurelius Victor 40.2&ndash;3; ''Epitome de Caesaribus'' 41.2; Zosimus 2.8.3; Eusebius, ''Vita Constantini'' 1.21; Lenski, "Reign of Constantine" (CC), 61; MacMullen, ''Constantine'', 32; Odahl, 73.</ref> It is uncertain how much these tales can be trusted.<ref>Lenski, "Reign of Constantine" (CC), 61.</ref>

===In the West===
Constantine  recognized the implicit danger in remaining at Galerius' court, where he was held as a virtual hostage. His career depended on being rescued by his father in the west. Constantius was quick to intervene.<ref>Odahl, 75&ndash;76.</ref> In the late spring or early summer of 305, Constantius requested leave for his son, to help him campaign in Britain. After a long evening of drinking, Galerius granted the request. Constantine's later propaganda describes how Constantine fled the court in the night, before Galerius could change his mind. He rode from post-house to post-house at high speed, mutilating every horse in his wake.<ref>Barnes, ''Constantine and Eusebius'', 27; Elliott, ''Christianity of Constantine'', 39&ndash;40; Lenski, "Reign of Constantine" (CC), 61; MacMullen, ''Constantine'', 32; Odahl, 77; Pohlsander, ''Emperor Constantine'', 15&ndash;16; Potter, 344&ndash;5; Southern, 169&ndash;70, 341.</ref> By the time Galerius awoke the following morning, Constantine had fled too far to be caught.<ref>MacMullen, ''Constantine'', 32.</ref> Constantine joined his father in Gaul, at Bononia (Boulogne) before the summer of 305.<ref>Barnes, ''Constantine and Eusebius'', 27; Elliott, ''Christianity of Constantine'', 39&ndash;40; Lenski, "Reign of Constantine" (CC), 61; Odahl, 77; Pohlsander, ''Emperor Constantine'', 15&ndash;16; Potter, 344&ndash;45; Southern, 169&ndash;70, 341.</ref>

thumb|right|Bronze statue of Constantine I in [[York, England, near the spot where he was proclaimed Augustus in 306]]
From Bononia they crossed the Channel to Britain and made their way to Eboracum (York), capital of the province of Britannia Secunda and home to a large military base. Constantine was able to spend a year in northern Britain at his father's side, campaigning against the Picts beyond Hadrian's Wall in the summer and autumn.<ref>Barnes, ''Constantine and Eusebius'', 27, 298; Elliott, ''Christianity of Constantine'', 39; Odahl, 77&ndash;78, 309; Pohlsander, ''Emperor Constantine'', 15&ndash;16.</ref> Constantius' campaign, like that of Septimius Severus before it, probably advanced far into the north without achieving great success.<ref>Mattingly, 233&ndash;34; Southern, 170, 341.</ref> Constantius had become severely sick over the course of his reign, and died on July 25 306 in Eboracum (York). Before dying, he declared his support for raising Constantine to the rank of full Augustus. The Alamannic king Chrocus, a barbarian taken into service under Constantius, then proclaimed Constantine as Augustus. The troops loyal to Constantius' memory followed him in acclamation. Gaul and Britain quickly accepted his rule;<ref name="N35">Barnes, ''Constantine and Eusebius'', 27&ndash;28; Jones, 59; Lenski, "Reign of Constantine" (CC), 61&ndash;62; Odahl, 78&ndash;79.</ref> Iberia, which had been in his father's domain for less than a year, rejected it.<ref>Jones, 59.</ref>

Constantine sent Galerius an official notice of Constantius' death and his own acclamation. Along with the notice, he included a portrait of himself in the robes of an Augustus.<ref>Barnes, ''Constantine and Eusebius'', 28&ndash;29; Lenski, "Reign of Constantine" (CC), 62; Odahl, 79&ndash;80.</ref> The portrait was wreathed in bay.<ref>Jones, 59; MacMullen, ''Constantine'', 39.</ref> He requested recognition as heir to his father's throne, and passed off responsibility for his unlawful ascension on his army, claiming they had "forced it upon him".<ref>Treadgold, 28.</ref> Galerius was put into a fury by the message; he almost set the portrait on fire. His advisers calmed him, and argued that outright denial of Constantine's claims would mean certain war.<ref>Barnes, ''Constantine and Eusebius'', 28&ndash;29; Lenski, "Reign of Constantine" (CC), 62; Odahl, 79&ndash;80; Rees, 160.</ref> Galerius was compelled to compromise: He granted Constantine and the title "Caesar" rather than "Augustus" (The latter office went to Severus instead).<ref name="GCA">Barnes, ''Constantine and Eusebius'', 29; Elliott, ''Christianity of Constantine'', 41; Jones, 59; MacMullen, ''Constantine'', 39; Odahl, 79&ndash;80.</ref> Wishing to make it clear that he alone gave Constantine legitimacy, Galerius personally sent Constantine the emperor's traditional purple robes.<ref>Odahl, 79&ndash;80.</ref> Constantine accepted the decision,<ref name="GCA"/> knowing that it would remove doubts as to his legitimacy.<ref>Barnes, ''Constantine and Eusebius'', 29.</ref>

==Early rule==
Constantine's share of the Empire consisted of Britain, Gaul, and Spain. He therefore commanded one of the largest Roman armies, stationed along the important Augusta Treverorum (adventus'' (arrival) celebrations that followed.<ref>Barnes, ''Constantine and Eusebius'', 29; Elliott, ''Christianity of Constantine'', 41; Lenski, "Reign of Constantine" (CC), 63; MacMullen, ''Constantine'', 39&ndash;40; Odahl, 81&ndash;83.</ref> 

thumb|right|[[Public bathing|Public baths (''thermae'') built in Trier by Constantine. More than  wide by  long, and capable of serving several thousands at a time, the baths were built to rival those of Rome.<ref>Odahl, 82&ndash;83.</ref>]]
Constantine began a major expansion of Trier. He strengthened the circuit wall around the city with military towers and fortified gates, and began building a palace complex in the northeastern part of the city. To the south of his palace, he ordered the construction of a large formal audience hall, and a massive imperial bathhouse. Constantine sponsored many building projects across Gaul during his tenure as Emperor of the West, especially in Augustodunum (Autun) and Arelate (Arles).<ref>Odahl, 82&ndash;83. See also: William E. Gwatkin, Jr. [http://penelope.uchicago.edu/Thayer/E/Roman/Texts/secondary/journals/CJ/29/1/Roman_Trier*.html Roman Trier]." ''The Classical Journal'' 29 (1933): 3&ndash;12.</ref> According to Lactantius, Constantine followed his father in following a tolerant policy towards Christianity. Although not yet a Christian, he probably judged it a more sensible policy than open persecution,<ref>Lactantius, ''De Mortibus Persecutorum'' 24.9; Barnes, "Lactantius and Constantine", 43&ndash;46; Odahl, 85, 310&ndash;11.</ref> and a way to distinguish himself from the "great persecutor" himself, Galerius.<ref>Odahl, 86.</ref> Constantine decreed a formal end to persecution, and returned to Christians all they had lost during the persecutions.<ref>Barnes, ''Constantine and Eusebius'', 28.</ref> 

Because Constantine was still largely untried and had a hint of illegitimacy about him, he relied on his father's reputation in his early propaganda: the earliest panegyrics to Constantine give as much coverage to his father's deeds as to those of Constantine himself.<ref>Rodgers, 236.</ref> Constantine's military skill and building projects soon gave the panegyrist the opportunity to comment favorably on the similarities between father and son, and Eusebius remarked that Constantine was a "renewal, as it were, in his own person, of his father's life and reign".<ref>''Panegyrici Latini'' 7(6)3.4; Eusebius, ''Vita Constantini'' 1.22, qtd. and tr. Odahl, 83; Rodgers, 238.</ref> Constantinian coinage, sculpture and oratory also shows a new tendency for disdain towards the "barbarians" beyond the frontiers. After Constantine's victory over the Alemanni, he minted a coin issue depicting weeping and begging Alemannic tribesmen&mdash;"The Alemanni conquered"&mdash;beneath the phrase "Romans' rejoicing".<ref>MacMullen, ''Constantine'', 40.</ref> There was little sympathy for these enemies. As his panegyrist declared: "It is a stupid clemency that spares the conquered foe."<ref>Qtd. in MacMullen, ''Constantine'', 40.</ref>

===Maxentius' rebellion===
Following Galerius' recognition of Constantine as emperor, his portrait was brought to Rome, as was customary. Maxentius mocked the portrait's subject as the son of a harlot, and lamented his own powerlessness.<ref>Zosimus, 2.9.2; Lenski, "Reign of Constantine" (CC), 62; MacMullen, ''Constantine'', 39.</ref> Maxentius, jealous of Constantine's authority,<ref>Barnes, ''Constantine and Eusebius'', 29; Odahl, 86; Potter, 346.</ref> seized the title of emperor on October 28 306. Galerius refused to recognize him, but failed to unseat him. During his first campaign against Maxentius, Severus' armies defected, and he was seized and imprisoned.<ref>Barnes, ''Constantine and Eusebius'', 30&ndash;31; Elliott, ''Christianity of Constantine'', 41&ndash;42; Lenski, "Reign of Constantine" (CC), 62&ndash;63; Odahl, 86&ndash;87; Potter, 348&ndash;49.</ref> Over the spring and summer of 307, he left Gaul for Britain to avoid any involvement in the Italian turmoil.<ref>Barnes, ''Constantine and Eusebius'', 30; Lenski, "Reign of Constantine" (CC), 62&ndash;63; Odahl, 86&ndash;87.</ref> Maximian, brought out of retirement by his son's rebellion, left for Gaul to confer with Constantine in late 307. He offered to marry his daughter Fausta to him, and elevate him to Augustan rank. In return, Constantine would reaffirm the old family alliance between Maximian and Constantius, and offer support to Maxentius' cause in Italy. Constantine accepted, and married Fausta in Trier in late summer 307. Constantine now gave Maxentius his meager support, offering Maxentius political recognition.<ref>Barnes, ''Constantine and Eusebius'', 31; Lenski, "Reign of Constantine" (CC), 64; Odahl, 87&ndash;88; Pohlsander, ''Emperor Constantine'', 15&ndash;16.</ref>

left|thumb|Dresden bust of Maxentius. Maxentius' rule in Italy worsened political relations within the Tetrarchy, and pushed its members towards open conflict.<ref>Odahl, 92.</ref> His ruling style and motivations have been likened to those of Constantine.<ref name = "leohak">Barnes, ''Constantine and Eusebius'', 37.</ref>

Constantine remained aloof from military conflict, however. Instead of sending his troops into a civil war, he sent them against Germanic tribes along the Rhine. In 308, he raided the territory of the Bructeri, and made a bridge across the Rhine at Colonia Agrippinensium (Cologne). In 310, he marched to the northern Rhine and fought the Franks. When not campaigning, he toured his lands advertising his benevolence, and supporting the economy and the arts. His refusal to participate in the war increased his popularity among his people, and strengthened his power base in the West.<ref>Barnes, ''Constantine and Eusebius'', 34; Lenski, "Reign of Constantine" (CC), 63&ndash;65; Odahl, 89; Pohlsander, ''Emperor Constantine'', 15&ndash;16.</ref> Maximian returned to Rome in the winter of 307&ndash;8, but soon fell out with his son. In early 309, after a failed attempt to usurp Maxentius' title, Maximian returned to Constantine's court.<ref>Barnes, ''Constantine and Eusebius'', 32; Lenski, "Reign of Constantine" (CC), 64; Odahl, 89, 93.</ref> 

On Severus, one of Galerius' old military companions, was appointed Augustus of the west. The new system did not last long: Constantine refused to accept the demotion, and continued to style himself as Augustus on his coinage, even as other members of the Tetrarchy referred to him as a Caesar on theirs. Maximinus was frustrated that he had been turned over for promotion while the newcomer Licinius had been raised to the office of Augustus, and demanded that Galerius promote him. Galerius offered to call both Maximinus and Constantine "sons of the Augusti",<ref>Barnes, ''Constantine and Eusebius'', 32&ndash;34; Elliott, ''Christianity of Constantine'', 42&ndash;43; Jones, 61; Lenski, "Reign of Constantine" (CC), 65; Odahl, 90&ndash;91; Pohlsander, ''Emperor Constantine'', 17; Potter, 349&ndash;50; Treadgold, 29.</ref> but neither accepted the new title. By the spring of 310, Galerius was referring to both men as Augusti.<ref>Barnes, ''Constantine and Eusebius'', 33; Jones, 61.</ref>

===Maximian's rebellion===
right|thumb|A gold multiple of Constantine with Sol Invictus, printed in 313. The use of Sol's image appealed to both the educated citizens of Gaul, who would recognize in it Apollo's patronage of [[Augustus and the arts; and to Christians, who found solar monotheism less objectionable than the traditional pagan pantheon.<ref>Barnes, ''Constantine and Eusebius'', 36&ndash;37.</ref>]]
In 310, a dispossessed and power-hungry Maximian rebelled against Constantine while Constantine was away campaigning against the Franks. Maximian had been sent south to Arles with a contingent of Constantine's army, in preparation for any attacks by Maxentius in southern Gaul. He there announced that Constantine was dead, and took up the imperial purple. In spite of a large donative pledge to any who would support him as emperor, most of Constantine's army remained loyal to their emperor, and Maximian was soon compelled to leave. Constantine soon heard of the rebellion, abandoned his campaign against the Franks, and marched his army up the Rhine.<ref name = "yuhknp">Barnes, ''Constantine and Eusebius'', 34&ndash;35; Elliott, ''Christianity of Constantine'', 43; Lenski, "Reign of Constantine" (CC), 65&ndash;66; Odahl, 93; Pohlsander, ''Emperor Constantine'', 17; Potter, 352.</ref> At Cabillunum (Chalon-sur-Saône), he moved his troops onto waiting boats to row down the slow waters of the Saône to the quicker waters of the Rhone. He disembarked at Lugdunum (Lyon).<ref>Barnes, ''Constantine and Eusebius'', 34.</ref> Maximian fled to Massilia (Marseille), a town better able to withstand a long siege than Arles. It made little difference, however, as loyal citizens opened the rear gates to Constantine. Maximian was captured and reproved for his crimes. Constantine granted some clemency, but strongly encouraged his suicide. In July 310, Maximian hanged himself.<ref name = "yuhknp"/> 

In spite of the earlier rupture in their relations, Maxentius was eager to present himself as his father's devoted son after his death.<ref>Elliott, ''Christianity of Constantine'', 43; Lenski, "Reign of Constantine" (CC), 68; Pohlsander, ''Emperor Constantine'', 20.</ref> He began printing coins with his father's deified image, proclaiming his desire to avenge Maximian's death.<ref>Elliott, ''Christianity of Constantine'', 45; Lenski, "Reign of Constantine" (CC), 68.</ref> Constantine initially presented the suicide as an unfortunate family tragedy. By 311, however, he was spreading another version. According to this, after Constantine had pardoned him, Maximian planned to murder Constantine in his sleep. Fausta learned of the plot and warned Constantine, who put a eunuch in his own place in bed. Maximian was apprehended when he killed the eunuch and was offered suicide, which he accepted.<ref>Lactantius, ''De Mortibus Persecutorum'' 30.1; Barnes, ''Constantine and Eusebius'', 40&ndash;41, 305.</ref> In addition to the propaganda, Constantine instituted a ''damnatio memoriae'' on Maximian, destroying all inscriptions referring to him and eliminating any public work bearing his image.<ref>Barnes, ''Constantine and Eusebius'', 41; Lenski, "Reign of Constantine" (CC), 68.</ref>

The death of Maximian necessitated a shift in Constantine's public image. He could no longer rely on his connection to the elder emperor Maximian, and needed a new source of legitimacy.<ref>Potter, 352.</ref> In a speech delivered in Gaul on July 25 310, the orator reveals a previously unknown dynastic connection to Claudius II, a third-century emperor famed for defeating the Goths and restoring order to the empire. Breaking away from tetrarchic models, the speech emphasizes Constantine's ancestral prerogative to rule, rather than principles of imperial equality. The new ideology expressed in the speech made Galerius and Maximian irrelevant to Constantine's right to rule.<ref>''Panegyrici Latini'' 6(7); Barnes, ''Constantine and Eusebius'', 35&ndash;37, 301; Lenski, "Reign of Constantine" (CC), 66; Odahl, 94&ndash;95, 314&ndash;15; Potter, 352&ndash;53.</ref> Indeed, the orator emphasizes ancestry to the exclusion of all other factors:  "No chance agreement of men, nor some unexpected consequence of favor, made you emperor," the orator declares to Constantine.<ref>''Panegyrici Latini'' 6(7)1. Qtd. in Potter, 353.</ref>

The oration also moves away from the religious ideology of the Tetrarchy, with its focus on twin dynasties of Jupiter and Victory granting him Ecologues'' 4.10.</ref> The oration's religious shift is paralleled by a similar shift in Constantine's coinage. In his early reign, the coinage of Constantine advertised Mars as his patron. From 310 on, Mars was replaced by Sol Invictus, a god conventionally identified with Apollo.<ref>Barnes, ''Constantine and Eusebius'', 36&ndash;37; Lenski, "Reign of Constantine" (CC), 67; Odahl, 95.</ref> There is little reason to believe that either the dynastic connection or the divine vision are anything other than fiction, but their proclamation strengthened Constantine's claims to legitimacy and increased his popularity among the citizens of Gaul.<ref>Barnes, ''Constantine and Eusebius'', 36&ndash;37; Elliott, ''Christianity of Constantine'', 50&ndash;53; Lenski, "Reign of Constantine" (CC), 66&ndash;67; Odahl, 94&ndash;95.</ref>

==Civil wars==
===War against Maxentius===

By the middle of 310 Galerius had become too ill to involve himself in imperial politics.<ref>Lactantius, ''De Mortibus Persecutorum'' 31&ndash;35; Eusebius, ''Historia Ecclesiastica'' 8.16; Elliott, ''Christianity of Constantine'', 43; Lenski, "Reign of Constantine" (CC), 68; Odahl, 95&ndash;96, 316.</ref> As his last political act, Galerius decided to rescind his failed policies of persecution. In a letter to his provincials posted in Nicomedia on Eusebius.<ref>Barnes, ''Constantine and Eusebius'', 38; Odahl, 96.</ref>

Maxentius' rule was nevertheless insecure. His early support dissolved in the wake of heightened tax rates and depressed trade; riots broke out in Rome and Carthage;<ref>Barnes, ''Constantine and Eusebius'', 37; Curran, 66; Lenski, "Reign of Constantine" (CC), 68; MacMullen, ''Constantine'', 62.</ref> and Domitius Alexander was able to briefly usurp his authority in Africa.<ref name = "leohak"/> By 312, he was a man barely tolerated, not one actively supported,<ref>Barnes, ''Constantine and Eusebius'', 37&ndash;39.</ref> even among Christian Italians.<ref>Barnes, ''Constantine and Eusebius'', 38&ndash;39; MacMullen, ''Constantine'', 62.</ref> In the summer of 311, Maxentius mobilized against Constantine while Licinius was occupied with affairs in the East. He declared war on Constantine, vowing to avenge his father's "murder".<ref>Barnes, ''Constantine and Eusebius'', 40; Curran, 66.</ref> Constantine, in an attempt to prevent Maxentius from forming a hostile alliance with Licinius,<ref>Barnes, ''Constantine and Eusebius'', 41.</ref> forged his own alliance with the man over the winter of 311&ndash;12 by offering to him his sister Constantia in marriage. Maximin considered Constantine's arrangement with Licinius an affront to his authority. In response, he sent ambassadors to Rome, offering political recognition to Maxentius in exchange for a military support. Maxentius accepted.<ref>Barnes, ''Constantine and Eusebius'', 41; Elliott, ''Christianity of Constantine'', 44&ndash;45; Lenski, "Reign of Constantine" (CC), 69; Odahl, 96.</ref> According to Eusebius, inter-regional travel became impossible, and there was military buildup everywhere. There was "not a place where people were not expecting the onset of hostilities every day".<ref>Eusebius, ''Historia Ecclesiastica'' 8.15.1&ndash;2, qtd. and tr. in MacMullen, ''Constantine'', 65.</ref>

thumb|right|The Porta Palatina ([[Palatine Towers), together with a stretch of the old city walls, where Constantine defeated Maxentius' troops in Turin]]

Constantine's advisers and generals cautioned against preemptive attack on Maxentius;<ref>Barnes, ''Constantine and Eusebius'', 41; MacMullen, ''Constantine'', 71.</ref> even his soothsayers recommended against it, stating that the sacrifices had produced unfavorable omens.<ref>''Panegyrici Latini'' 12(9)2.5; Curran, 67.</ref> Constantine, with a spirit that left a deep impression on his followers, inspiring some to believe that he had some form of supernatural guidance,<ref>Curran, 67.</ref> ignored all these cautions, and attacked Maxentius without a ''Susa, Italy), a heavily fortified town containing a military garrison, which shut its gates to him. Constantine ordered his forces set its gates on fire, scaled its walls, and took the town quickly. Constantine forbade the plunder of the town, and advanced into northern Italy.<ref name = "esyyqc"/> 

At the approach to the west of the important city of Augusta Taurinorum (battle Constantine encircled Maxentius' cavalry, flanked them with his own cavalry, and dismounted them with blows from his soldiers' iron-tipped clubs. Constantine's armies emerged victorious.<ref>''Panegyrici Latini'' 12(9)5&ndash;6; 4(10)21&ndash;24; Jones, 70&ndash;71; MacMullen, ''Constantine'', 71; Odahl, 102, 317&ndash;18.</ref> Turin refused to give refuge to Maxentius' retreating forces, opening its gates to Constantine instead.<ref>Barnes, ''Constantine and Eusebius'', 41; Jones, 71; Odahl, 102.</ref> Other cities of the north Italian plain sent Constantine embassies of congratulation for his victory. He moved on to Milan, where he was met with open gates and jubilant rejoicing. Constantine rested his army in Milan until mid-summer 312, when he moved on to Brixia (Brescia).<ref>Barnes, ''Constantine and Eusebius'', 41&ndash;42; Odahl, 103.</ref>

Brescia's army was easily dispersed,<ref>Barnes, ''Constantine and Eusebius'', 42; Jones, 71; MacMullen, ''Constantine'', 71; Odahl, 103.</ref> and Constantine quickly advanced to encounter that followed, Ruricius was killed and his army destroyed.<ref>Barnes, ''Constantine and Eusebius'', 42; Jones, 71; Odahl, 103&ndash;4.</ref> Verona surrendered soon afterwards, followed by Aquileia,<ref>Barnes, ''Constantine and Eusebius'', 42; Jones, 71; Lenski, "Reign of Constantine" (CC), 69; MacMullen, ''Constantine'', 71; Odahl, 104.</ref> Mutina (Modena),<ref>Jones, 71; MacMullen, ''Constantine'', 71.</ref> and Ravenna.<ref>MacMullen, ''Constantine'', 71.</ref> The road to Rome was now wide open to Constantine.<ref>Barnes, ''Constantine and Eusebius'', 42; Curran, 67; Jones, 71.</ref>

thumb|right|The Milvian Bridge ([[Ponte Milvio) over the Tiber, north of Rome, where Constantine and Maxentius fought in the Battle of the Milvian Bridge]]
Maxentius prepared for the same type of war he had waged against Severus and Galerius: he sat in Rome and prepared for a siege.<ref>Barnes, ''Constantine and Eusebius'', 42; Jones, 71; Odahl, 105.</ref> He still controlled Rome's praetorian guards, was well-stocked with African grain, and was surrounded on all sides by the seemingly-impregnable Aurelian Walls. He ordered all bridges across the Tiber cut, reportedly on the counsel of the gods,<ref>Jones, 71.</ref> and left the rest of central Italy undefended; Constantine secured that region's support without challenge.<ref>Odahl, 104.</ref> Constantine progressed slowly,<ref name="BCE42">Barnes, ''Constantine and Eusebius'', 42.</ref> along the ''Via Flaminia'',<ref>MacMullen, ''Constantine'', 72; Odahl, 107.</ref> allowing the weakness of Maxentius to draw his regime further into turmoil.<ref name="BCE42"/> Maxentius' support continued to weaken: at chariot races on October 27, the crowd openly taunted Maxentius, shouting that Constantine was invincible.<ref>Barnes, ''Constantine and Eusebius'', 42; Curran, 67; Jones, 71&ndash;72; Odahl, 107&ndash;8.</ref> Maxentius, no longer certain that he would emerge from a siege victorious, built a temporary boat bridge across the Tiber in preparation for a field battle against Constantine.<ref>Barnes, ''Constantine and Eusebius'', 42&ndash;43; MacMullen, ''Constantine'', 78; Odahl, 108.</ref> On October 28 312, the sixth anniversary of his reign, he approached the keepers of the Sibylline Books for guidance. The keepers found in them a prophecy stating that, on that very day, "the enemy of the Romans" would die. Maxentius advanced north to meet Constantine in battle.<ref>Lactantius, ''De Mortibus Persecutorum'' 44.8; Barnes, ''Constantine and Eusebius'', 43; Curran, 67; Jones, 72; Odahl, 108.</ref>

Maxentius organized his forces&mdash;still twice the size of Constantine's&mdash;in long lines facing the battle plain, with their backs to the river.<ref name = "bvubfs">Odahl, 108.</ref> When Constantine's army made its appearance, some of its soldiers bore unusual markings on their shields: instead of the traditional pagan standards, a new sign, the ''Chi (Χ) traversed by Rho (Ρ), or ☧.<ref>Barnes, ''Constantine and Eusebius'', 306; MacMullen, ''Constantine'', 73; Odahl, 319.</ref> The Eusebian description of the vision has been explained as an example of the meteorological phenomenon known as the "solar halo", which can produce similar effects.<ref>Barnes, ''Constantine and Eusebius'', 306; Cameron and Hall, 206&ndash;7; Drake, "Impact of Constantine on Christianity" (CC), 114; Nicholson, 311.</ref>

right|thumb|''[[The Battle of the Milvian Bridge (Giulio Romano)| The Battle of the Milvian Bridge'' by Giulio Romano]]
Constantine deployed his own forces along the whole length of Maxentius' line. He ordered his cavalry to charge, and they broke Maxentius' cavalry. He then sent his infantry against Maxentius' infantry, pushing many into the Tiber where they were slaughtered and drowned.<ref name = "bvubfs"/> The battle was brief:<ref>Barnes, ''Constantine and Eusebius'', 43; Curran, 68.</ref> Maxentius' troops were broken before the first charge.<ref>MacMullen, ''Constantine'', 78.</ref> Maxentius' horse guards and praetorians initially held their position, but broke under the force of a Constantinian cavalry charge; they also broke ranks and fled to the river. Maxentius rode with them, and attempted to cross the bridge of boats, but he was pushed by the mass of his fleeing soldiers into the Tiber, and drowned.<ref>Barnes, ''Constantine and Eusebius'', 43; Curran, 68; Lenski, "Reign of Constantine" (CC), 70; MacMullen, ''Constantine'', 78; Odahl, 108.</ref> 

שמאל|ממוזער|150px|הקיסר קונסטנטינוס
'''גאיוס פלביוס ואלריוס אאורליוס קונסטנטינוס''' (בקיסר הקיסרות הרומית המערבית משנת 312, עד 324, וקיסר האימפריה הרומית כולה משנת 324, עד למותו בשנת 337.

קונסטנטינוס נודע בעיקר בשל פעילותו לקידום מעמדה של הנצרות באימפריה הרומית, שהובילה לקבלתה כדתה הרשמית של האימפריה.
== ביוגרפיה ==
===נעורים וקריירה מוקדמת===
שמאל|ממוזער|380px|מטבע שנטבע בימי שלטון קונסטנטינוס, עליו מופיע דיוקנו
קונסטנטינוס נולד בנאיסוס להלנה. אמו הייתה נוצריה וממנה קיבל את היכרותו הראשונית עם הדת הנוצרית. בשנת 293 מונה על ידי אביו לאחד מקיסרי הטטררכיה, ושירת בחצרו של דיוקלטיאנוס בניקומדיה.

===תפיסת השלטון===
בשנת 310, לאחר פרישת דיוקלטיאנוס ושותפו מהנהגת רומי בשיטת הטטררכיה בשנת 305, קמו שישה טוענים לרשת את כס השלטון.
ביניהם היה קונסטנטינוס, שלאחר מות אביו צבאו לאחר שזה הכריז עליו כיורשו, אל עבר רומא שהייתה בשליטתו של מקסנטיוס.

על פי המסורת הנוצרית, ערב הקרב שהתרחש ב-חלומו, והתקין על מגיני החיילים את סימן הצלב, ופנה לכבוש את רומא, וליטול לידיו את תואר קיסר רומי המערבית.

חוקרים רבים חלוקים בדעתם מדוע בחר לו קונסטנטינוס לחסות בצל הנצרות, דת שסבלה עד זמן קצר לפני תקופתו מרדיפות על ידי השלטונות, והייתה דת חדשה באופן יחסי שזכתה עדיין ליחס חשדני ועוין. ההשערות הרווחות במחקר מעלות כי קונסטנטינוס הבין כי הנצרות תסייע לו לאחד את האימפריה הרומית תחת דת אחת, שהוא עומד כפטרונה הראשי, במקום הפילוג שהיה באותה עת ברחבי האימפריה. כמו כן, חוקרים מסוימים סבורים כי קונסטנטינוס זיהה את ישו כאל השמש, דבר שאכן בא לידי ביטוי בנצרות, כשלאחר מכן השתרשו בה סממנים פאגנים רבים, וסגידה לאל השמש בפרט, כדוגמת בחירת יום ראשון (שיוחס במסורת הרומית לאל השמש) כיום המקודש לנצרות, וציון הולדתו של ישו ב-25 בדצמבר, שעל פי האמונה הפאגנית זהו יום הולדתו של אל השמש, שכן יום זה הוא היום הקצר בשנה ובו חל מפנה במהלך השמש.

אמונתו הפאגנית של קונסטנטינוס באה לידי ביטוי גם בהטבעת סמלים פגאניים על מטבעותיו. למעשה, קונסטנטינוס כלל לא הוטבל לנצרות, אלא רק כשכבר היה על ערש דווי, על ידי אאוזביוס מניקומדיה. לכן, חוקרים רבים מעריכים כי קונסטנטינוס תמך בשתי האמונות על מנת להגדיל את כוחו באימפריה.

מסורת נוצרית מאוחרת יותר מייחסת את הטבלתו לנצרות לאפיפיור סילבסטר הראשון, כמו גם את ריפויו ממחלת הצרעת, אם כי אין לה ביסוס - קונסטנטינוס נטבל למעשה רק על ערש מותו, בשנת 337, כאשר האפיפיור סילבסטר כבר היה מת זה כשנה וחצי. ייתכן שהמקור לאגדה זו הוא ברצון להצניע את העובדה שקונסנטינוס, מיטיב הנצרות, למעשה לא קיבל על עצמו את הנצרות עד לסוף חייו.

====צו מילאנו====

לאחר שהתברר כי הקיסר החדש נוטה חסד לנצרות, מיהרו אלו להציע את שירותם לקונסטנטינוס כיועצים, מדריכים רוחנים לו, ומחנכים לבנו. בעקבות כך, ובשל הכרת הטוב לדתו החדשה ש"סייעה" לו לנצח בקרב על רומא, פרסם כשנה לאחר מכן בשנת 313, בשיתוף עם קיסר המזרח גלריוס, הכרזה בשם צו מילאנו, שבה קרא כי מן הראוי שהאימפריה הרומית תפגין סובלנות מלאה כלפי כל אדם שבחר להאמין בנצרות, או בכל כת אחרת, ובנוסף, קרא לתיקון העוולות שנעשו לנוצרים במהלך רדיפתם. בכך שם קונסטנטינוס קץ לרדיפת הנצרות, וחיזק את מעמדה כדת לגיטימית, ואף מועדפת ברחבי האימפריה.

====ועידת ניקיאה====

בשנת וועידה האקומנית הראשונה של הכנסייה. הכנסייה התכנסה בעיר ניקיאה שבאסיה הקטנה (היום איזניק). קונסטנטינוס זימן את מנהיגי כל הקהילות הנוצריות, על מנת לדון במדיניות הכנסייה וקביעת הדוקטרינה הנוצרית. הוא קיווה שבכך ישים קץ  למחלוקות הרבות שבתוך הנצרות, ובכך, ליצור מצב שבו ישנו '''"אל אחד, דת אחת"''' כדי לגבש את תביעתו ל'''"אימפריה אחת, קיסר אחד"'''.

בסופה של ועידה זו, שנודעה בשם "ועידת ניקיאה", הוכרז כי האריאנים שהתנגדו לשילוש הקדוש, הם כופרים. ופירסמו את ה"אני מאמין" או בשמו האחר ה"קרדו של ניקיאה".

===פעולות נוספות===

בנוסף לבניית ערים רבות שהנציחו את שמו, הגדיל לעשות קונסטינוס, כשבשנת 330 העביר את בירת האימפריה הרומית מרומא - לקונסטנטינופול, ואגב כך עורר מחלוקת בין שתי הבירות בנוגע לבכורה הרוחנית.
מלבד בניית ערים, בנה קונסטנטינוס כנסיות רבות, כשהמפורסמת והחשובה מביניהם היא כנסיית הקבר הקדוש.

==מתת קונסטנטינוס==

מסמך מזויף בשם מאה השמינית, טען שקונסטנטינוס העניק לסילבסטר סמכות על הפרובינציות הרומאיות, ושימש את האפיפיורות להצדקת התערבותם המדינית בימי הביניים. המסמך הואשם בהיותו מזויף לראשונה על ידי הקיסר מאה העשירית, האשמה שהוכחה כנכונה בתקופת הרנסאנס, על ידי לורנצו ואלה, על ידי בחינת השפה בה הוא נכתב.

==יחסו ליהודים==

ביהדות מוצג קונסטנטינוס לעתים באור שלילי, בניגוד לתדמיתו החיובית בנצרות. כמי שתרם לביסוס מעמדה של הנצרות באימפריה הרומית והפיכתה לדת מרכזית, הוא מואשם ברדיפות היהודים שהתקימה על ידי הכנסייה לדורותיה, על אף שזו החלה רק לאחר תקופתו.