Constantine I, the Great, Born 272 AD(?), Died 337 AD
End of 3rd century, beginning of 4th,
Acclaimed at Eboracum (later, York), 306 AD

Timeline
 
272 AD
Possible Year of Constantine's birth in Naissus (now Nis in  Southeast Serbia)

306 AD
Constantius I Chlorus, father of Constantine Dies,
Constantine acclaimed by legions in York

308
Constantine accepted as Caesar of the west

312
Roman Emperor Constantine tolerates Christianity,
Constantine defeats Maxentius at Saxa Rubra, Milvian Bridge,
Constantine disbands Maxentius's Praetorian Guard,
Constantine reduces the cohortes urbanae of Rome

313
Basilica of Maxentius completed by Constantine,
Constantine promulgates the Edict of Milan

c. 315
Arch of Constantine built to Commemorate Milvian Bridge Battle of 312

315
Baths of Constantine completed in Rome

324

Constantine defeats Licinius at Chrysopolis, September, 
Constantine rehabilitates his mother Helena, "Augusta",
Constantine makes wife Fausta, "Augusta" 

325
Constantine, "Roman Emperor", calls Council of Nicea

326
Scandal, executions of Crispus, his son and Fausta, wife

330, May 11
Constantinople, "New Rome", founded on site of Byzantium

337
Constantine is Baptized and dies
   




Constantine I, the Great.
(278(?) to 337)


Prelude:  Constantine's father

 

Constantius I Chlorus
  


Constantine I, the Great.
This colossal head was used to set the scale of a replica statue and both were installed in the Roman  Capitoline Museum in 2024.
(note that the little dark splodge in the lower right corner of the picture is a person. It gives you an idea of the size of the original and replica statues
  

Flavius Valerius Constantius (c. 250 – 25 July 306), also called Constantius I, was a Roman emperor from 305 to 306. He was one of the four original members of the Tetrarchy established by by Diocletian, first serving as Caesar from 293 to 305 and then ruling as Augustus until his death.

Constantius was also the father of Constantine I, the Great, the first Christian emperor of Rome.  The  nickname Chlorus, meaning "the pale" was first applied and popularized by Byzantine era historians and was not used during his lifetime. 

Constantius, was a commoner whose exemplary military career had allowed him to rise to the top ranks of the Roman army.  During his rise he had met and become involved with a woman named Helena, who may have been a "hostess" that Constantius met in an establishment of low repute, while on duty out east.

The Helena story, which comes to us only through Christian secondary sources, states that she and Constantius were married, but marriage as defined in ancient Rome had several forms, the least of which involved just living together and having intimate relations, concubinage or Common Law Marriage.

Their relationship produced a male child who eventually became Emperor Constantine I, The Great.
Helena Augusta

 In 2023, parts of the colossal statue of Constantine that once stood in the even more colossal Basilica of Maxentius in Rome were used to set the size of a full scale 13 meter high sitting replica of the original.  All the artifactual stone parts and the new (mostly plastic) 13 replica were put on display in the Capitoline Museum in 2024.
But then,  To increase the possibility of his utmost promotion,
 Constantius I Chlorus put aside the lower class, and therefore somewhat embarrassing, concubine Helen to marry Theodora the daughter of Maximiam. 
Diocletian
The plan was that Diocletian, the reigning Emperor, was to split the Emperorship with Maximian, who had had great military successes, and that both Diocletian and Maximian would have the title "Augustus", and both would have subsidiary partners, with whom they would share their power. Each of the lesser rulers would be called a "Caesar".  All four rulers were called tetrarchs and the quadruple rule was called Tetrarchy.

Maximian and Diocletian were related by blood and marriage and called each other "brothers", and they each adopted their Caesars to ensure inheritance and succession.

  Maximian

Tetrarchy (est 293 AD):  The empire would be divided into four semi-independant segments, each with its own ruler and powers of decision and war making and with its own bureaucracy. The rulers, of course, should all and always be collegial, would hopefully coordinate their plans, step on each others toes as rarely a possible, and, most importantly Diocletian would be the boss -- unless he retired

The eastern half of the greater Empire would be ruled by Diocletian himself, using Nicomedia as his capital, and would have the title of "Augustus" of the east.  Diocletian would divide his half with a junior "Caesar", Galerius, who would have his own capital in Sirmium.

Maximian, the Augustus for the western half, would set up in Mediolanum (Milan), and his junior Caesar, his son-in-law, (inevitably), Constantius I Chlorus, would have his headquarters in Augusta Treverorum (Trier).

All four of the power centers were chosen because of proximity to trouble either near the Italian political center or facing threatened border areas.




                                                                  --------->
Porphyry statue (ca. 300 AD) depicting Tetrarchs.

Not like earlier Roman portrait statues in faces, attributes, nor physiques.

Looted from Constantinople in 4th Crusade, 1404, by the Venetians.

Now mounted on outside corner of the Treasury of St. Mark Cathedral, Venice.

The treasury holds much other Constantinople loot.
   
Map of Diocletian's Tetrarchy

Four colors, four ruling areas -- Tetrarchy
The first half of Tetr arch is Greek meaning four, second half means ruler.

GREEN -- Diocletian, Augustus
BLUE -- Maximian, Augustus
PINK -- Galerius, Caesar
PURPLE -- Constantius I, Caesar

    But Diocletian did retire!  In 305 AD Diocletian decided that he, as well as the other Augustus, Maximian, should retire from ruling and leave supreme power to the two Caesars.  Diocletian had been seriously ill in 304and famously was quoted as saying he wanted to pursue his retirement in Split (in modern Croatia) where he wanted to grow cabbages. 

When Diocletian retired there was nobody with the auctoritas to keep the tetrarchy from going off the rails.  Everyone tried to call him back, but he uttered the famous cabbage quote.
Diocletian's quote, found in various historical sources including Aurelius Victor's Epitome de Caesaribus, reflects Diocletian's decision to abdicate the throne and retire to his palace in Split, Croatia, to cultivate his gardens and live a peaceful life.		    
Diocletian's Split Palace visualized as completed in 305 AD, suitably surrounded by gardens and also with several green yards inside.  Cabbages?

  
When Diocletian and Maximian laid down the Purple in 305, both "Caesars", i.e., junior emperors became "Augustes", senior emperors.  Constantius had recenty put down two pretenders to the Imperial mandate, one in Gaul and one in Britania, both of whom actually started their pretense in Britania.  He then campaigned against the Picts (painted Scotsmen) of the far north of Britania. 

Having defeated the Picts he went back to Erboricum, York.  With him in his many victories and in his armies' winter quarters in York was Constantine, his son with Helena,

A tacit agreement had been reached among the Tetrarchs that Constantine, now a seasoned and well respected warrior general, would be one of the new Caesars, and that the other would be Maxentius, the son of Maximian.

Constantius I Chlorus never left his winter quarters. He died of fever(?) in July of 306, the year after he had become an Augustus.

On his death bed Constantius is said to have recommended Constantine to the legions at York as his sucessor.  The legions agreed, and Constantine was quickly declared emperor by the several legions occupying Britania, and he prepared to march southward.		   

Constantine I,
the Great


Statue in York, England, bronze, 1998, by Scotish scuptor Philip Jackson, located in the Minster Yard, outside York Minster, near where Constantine's father, Constantius I, died ,




Constantine had served with distinction under Diocletian and Galerius.      
His career started in campaigns in the east against the Persians but he was soon at his father's side fighting Picts in northern Britania and undoubtedly pushing further north into their Highland territory -- north of the former Antonine line.  Constantine was definitely what we could today call a "nepo-baby", but his actions in the field had quickly earned the respect of the occupying legions.  (The northward push had little permanent result.  Constantius won his requisite victories and Constantine won local legionary respect, but Picts kept coming.)
 



Galerius Augustus



  
We now get into some dicey "history".  This is the usual version:

When Diocletian and Maximian had retired at the beginning of May, 305 AD, after a serious Diocletian medical scare, many thought that Diocletian would announce that Maxentius and Constantine, the sons of Maximian and Constantius would rise to become the two new "Caesares", the junior emperors.  In the event, Diocletian, instead, gave the Caesar laurels to Severus and Maximinus, while promoting Constantius and Galerius to the offices of Augustus.

Constantine was in the military service of Galerius Augustus, who was said to be jealous and afraid of Constantine's popularity and "nepo-baby" status.  Stories had started circulating that Galerius had more than once plotted, during the months after Diocletian abdicated, to put Constantine into perilous assignments, attempting to kill him on hunts or in battle.  It is not certain whether any of these stories can be trusted.

If true or not, the stories further say that Constantine and his father saw the danger in what amounted to a hostage situation, and that Constantius won (in some versions, after a heavy drinking bout with with Galerius) permission for Constantine to join him in Britania. 

This led, according to the story, to a midnight horseback dash away, before Galerius might sober up.  Constantine used post horses that he hamstrung after use to slow pursuit.  When Galerius awoke, Constantine was to far out of reach to catch, on his way to Bononia (Boulogne) in Gaul, where he joined Constantius, and they both shortly after debarked safely in Britania and started chasing Picts.

Constantine and Galerius were already at odds.

 

The Laurel Nobilis crown was a common prize for winning a race in the Greek Games and was adopted as a more general sign of Victory (along with a palm frond and/or a tripod on which incense could be burned).  Constantine thereafter favored the Laurel Nobiis crown.  His Gold Aureus set the pattern for coinage, although more democratic regimes might show a laurel wreath not worn as a diadem.  Pictures of him usualy show him wearing a gold Laurel Nobilis diadem

Most species of laurel are poisonous, but Laurel Nobilis is the same bay leaf we put in our pasta sauce -- edible and pleasant smelling, and enough might cover the odor of a sweaty runner.
   In July of 306, Constantius I was dead and Constantine had been acclaimed as Augustus by the legions in Britania.

Constantine sent Galerius an official notice of the occurences and, along with the letter, a portrait of himself wearing the distintive robes of an Augustus.  And the portrait was wreathed in bay (laurel nobilis), a victor's crown (originally in the Games).  Constantine explained in his letter that he had to accede to the honor: the legions had "forced it upon him". 

Galerius, of course, was furious:  Constantine's letter was an insult, and the wreathed portrait was clearly a middle-finger salute.  (Yes, Romans really did that.)

Galerius, realizing that a war could start immediately if he responded immoderately, and knowing that he was himself  pretty unpopular, allowed his advisors to talk him down out of his anger and responded by sending Constantine a set of the robes of a Caesar.  Having received back another middle-finger salute, Constantine also decided not, for the moment, to press his claim -- fo now.


    Meanwhile back in Rome:  After Galerius recognized Constantine as a Caesar a portrait, as was customary, was sent to Rome.  Maxentius, still fuming at not being raised to the rank of Caesar in Diocletian's valedictory, mocked Constantine including by referring to him as a son of  harlot.  A few months later, on October 28, 306, Maxentius seized the title of emperor, which the Roman Senate approved, but the Tetrarchs denied.

Galerius would not recognize Maxentius but couldn't depose him.  Severus was sent to try in April of 307, but his legions that had previously been under the command of Maximian, the father of Maxentius, defected en masse: Severus was captured and jailed.

Maximian, who had been Diocletian's co-Augustus, came out of retirement to undertake a diplomatic mission to Constantine in Gaul to renew relations between the two families.

Part of the deal of mutual recognition between Constantine and Maxentius would be marriage between Constantine and Fausta, the daughter of Maximian and sister of Maxentius in 307 AD in Trier. 

The wedding apparently was or it developed into a love match.  In 310, Fausta had to make a choice between family and husband.  When Maximian tried to involve her in a plot to kill Constantine, she quickly told Constantine the details. 

As a result, Maximian either was killed or was forced to suicide leading to the defeat/decline of Maximian's and her own family. 

In 324 AD Constantine made Fausta an Augusta, a sign of great esteem and regard. 

  
Maxentius
Fausta, daughter of
Maximian and sister of Maxentius

But, two years later, a great scandal.  Possibly to advance her own pre-Constantine son, she supposedly accused Constantine's pre-Fausta son and heir apparent, Crispus, of rape. Angry, Contantine was said to have had Crispus poisoned.

Then doubts were raised.  Did she just make up the whole story?  Maybe Constantine believed that she did make it up.  He is said to have had her locked inside an overheated bath until she expired.  Or perhaps Crispus really did or really tried to rape Fausta. 

Or could she have tried to seduce him and was rejected.

Or maybe they were just caught in or were wrongly accused of adultery. 

Pehaps caught in incest(?), but no real blood relationship.

"Experts and scholars" still can not / will not agree.

But experts and scholars mostly do agree that Crispus and Fausts both were killed and in short order.  The stories or conjectures about the affair have sticking and staying and traveling power.  The image shows an Arabic version of in flagrante and accuses Fausta.


Crispus in red,
Fausta in blue

Constantine inherited Britain, Gaul, and Spain, and his first job was to get them back under control.  his father had quelled two military revolts. 

Carausius had sprung from the Roman Britanic Fleet (classis Britanicus) and, after gathering some support in the land legions, managed to set up a short lived independent "Roman" state -- not ruled from "back home" but ruled by Romans in Britania.  He had some elite Celtic support but most Celts were still under repressive Roman miltary occupation.
 
He ran the Roman Fleet anti-piracy off Spain but was accused of taking action only after the pirates had already captured and looted merchant shipping and then accumulating the booty for himself and his crews.  When Maximian ordered the death of Carausias, he and his henchmen came ashore and set up a rebel "Roman" regime with him taking the title of Augustus.  Some locals thought his government was more easy to deal with than the official Roman government.  He successfuly recruited among these friendlies, trained them as seamen and quickly got contol of some mainland and Britainic Gauish ports and the seas in between them and Britania. 

Maximian and Diocletian had tried to dislodge Carausius, but it was Constantius who eventually (293) drove Carausius from Gesoria, his European continental base after the two Augustuses had granted quasi-recognition in 290.  Also in 293, Carausius, who was still at large, was assassinated in a plot led by his own "finance minister" Allectus, who then ran the rebel operation for another three yaers. 

Allectus took over, but there is little record of his three years  The money man counted but his bureaucracy was less literate than those of the early days, and to the people opposing them it was all about body count. 

Constantious I Chlorus had viewed his own first job  when he came to command this part of the province would be rehabilitating a rebelious legion, then using it and others to bring the locals back under control both in Britania and in northern and western Gaul.  Constantine meanwhile was earning. his battle awards further into the mainland at fortified river borders, keeping the wooden mainland Eufopean limites up and running with occasional forays northward and westward to keep the locals honest and to keep the Legions sharp.  (You have to really fight to stay good at fighting.  Just practicing fighting is also needed, but if there is no danger of death it's just playing. 

Now we've seen that, by the time Constantine got free of Galerius and joined his father, Britain could look forward to a fairly prosaic period.  Not much was going to happen here.  The excitement would have been elsewhere, i.e., on the mainland.  Rebel coin issue, in western Gaul from the Allectus period have been  found only where his group was still able to be active (on the mainland) and that is where  Constantius had found and eliminated Allectus, leaving only Picts, a perennial problem, which would remain that, for Constantine to address

 
Constantine's first chore, after his acclamation and accession was to intimidate the picts to limit their activity while he left the province so he could unify and Christianize the Roman World.  It took Constantine only a short time to drive back the remaining picts and secure his control over the northwestern Dioceses. 
"Picts" because they covered
themselves with Pictues
 

 

A large part of this was construction work rather than fighting. as always, his legions built and rebuilt roads and forts, often completing work that his father had started but had to interupt because those same legionaries had been needed to root out Carausius and Allectus.  		Legions routinely built and repaired in their "spare time"

Franks
  


When all was finally complete he could leave for Augusta Treverorum, Trier in Gaul,  the Tetrarchic northwest capital.  Constantine had been acclaimed in 306, and, learning this, the Frankish tribes crossed the Rhine in the winter of 306-307.  Constantine arriving at Trier quickly drove them back capturing Frankish co-ruler Ascaric and Merogais. They and other captives were fed to the beasts of the Trier Amphitheater at Constantine's arrival ceremony, his Adventus.

Then it was back to construction work, now in Gaul, Constantine and legionary engineers planning and troopers strengthening Trier's circuit walls, adding towers, and refortifying gates, and most importantly, building Trier into a suitable capital for the western empire.  See https://www.rlp-tourismus.com/en/experience/culture/stories/emperor-constantine-and-roman-trier

Constantine stayed in Trier for six years before moving against Maxentius.
Constantine's Trier

Then the real action started.  Rather than repeat the civil wars of the Tetrarchs here I recommend the following Internet site:  https://en.wikipedia.org/wiki/Civil_wars_of_the_Tetrarchy

Saxa Rubra and the Milvian Bridge
Prelude:  The famous light in the sky -- everyone saw it, Constantine used it.

There is still controversy about what Constantine and many others in his entourage saw in the sky while marching toward Rome.  People of strong faith, remarkably many, still believe that a miracle occured that was planned by God to convert Constantine to Christianity.  Many others, increasingly many, say the vision was a natural phenomenon that was misinterpreted either as an act of faith or as a purposeful act of manipulation.  There are two favorite theories of what natural phenomena could have caused the "vision".
 Parhelia or "Sun Dogs" are something like a rainbow, but
requiring high thin Cirrus clouds (i.e. clouds of six sided tiny ice crystals) and low temperatures rather than falling raindrops between the observer and the sun.  There is more likelihood of seeing the full circle if you are on a down-slope of a mountain moving toward the sun. 

Superstitious minds see a miracle, and if one is predisposed to see a Christian symbol (e.g., Chi-Rho  or PX) and if conditions only let the right side of the Parhelia light-show visible, it might impress.  See https://en.wikipedia.org/wiki/Sun_dog

[Parhelia can also be a bane to high altitude pilots.  it's hard enough to have one sun in your field of vision.  On the other hand, parhelia also can alert you to lots of ice crystals in the clouds ahead]

 Sirente bolide: in the late 20th century, it was proposed that what Constantine saw was a meteor which entered the Earth's atmosphere over central Italy and either exploded violently (changing its classification to "bolide") or crashed into the surface in one piece and caused "splashing" of molten rock that caused minor craters beyond the larger initial Sirente Crater (together, the Sirente Crater Field).  In either case what would have been visible to ground observers would be a very bright streak of light (day or night) followed by a smoke/particle trail followed by an extremely widely visible impact explosion (calculated, by the size of the main Sirente Crater, at minimum 1 kiloton), a fireball, and a brightly lit mushroom cloud.  That would also impress (again, day or night).

Timing would be critical: this was a one-off event, but within the possible range of vision of a marching column for more than the time it would take to actually occur.  Modern research puts Constantine's march southward toward Saxa Rubra and the Milvian Bridge within the calculated range of the actual strike date and distance. If it happened near the end of their march, they could have seen it.  Sirente is 85 miles east of Saxa Rubra.  See https://en.wikipedia.org/wiki/Sirente_crater

So Constantine saw something that he said impressed him, he told his probably Mithra-worshiping troops it was a Christian sign (the Chi-Rho, later called the "ChristoGram": Chi and Rho being the first two letters of his name) and that they should paint it on the shields and march into Saxa Rubra, one of the most famous although misnamed  battles ever.
  
So Constantine is marching southward through Italy winning battles and accepting defection of cities and forces supposedly controlled by Maxentius, who is still, however, safe inside of Rome.  Maxentius is inside the walls with more than double the troop strength of Constantine -- probably a 100,000 to 40,000 advantage.

Maxentius had taken advantage of the time it took for Constantine to march down from Trier, cross the Alps, and fight his way down through Italy to over-stock Rome with food and water, more than enough to withstand a siege. And he was behind Aurelian's massive walls that would not really be breached until struck by heavy gunpowder artillery in 1870. 
 
On September 20, 1870, the last stage of the Italian Resorgimento (Re-unifiation) started to play out just outside of Porta Pia in a southeast facing section of of Aurelian's walls. 

Aurelian had included a servicible gate about one hundred meters southward down the wall, but, during the Renaissance, a new street, Via Pia, had been built running between a papal residence (today's Italian Presidential residence) and the wall.  At the wall a new Porta Pia was commissioned by Pope Pius IV Medici and designed, as one of his last works, by Michelangelo.  Porta Pia became an operating Gate to Rome in 1851.

In 1870 all that stood in the way of the northern Italian Bersaglieri military unit that was tasked with blasting their way into Rome and chasing the Pope out of his Palace, was Porta Pia.  Not wanting to destroy Michelangelo's last monumental architectural work, they aimed their artillery at the Aurelian wall, between Aurelian's previous gate (Porta Nomentana) and Porta Pia and finally actually breached the wall.  One unexploded and still considered very dangerous shell is still embedded nearby in the wall.  Rome had indeed been taken more than once after Aurelian, but always by trickery or treachery. 

Via Pia's name is now Via Sept. 20.



Michelangelo's Porta Pia now houses the Bersaglieri memorial and Museum

Back to Constantine.
Military experts and worldwide War College curricula all agree that Maxentius should have stayed inside the city walls to outlast any siege.  He, in fact, had already previously done so when besieged by other Tetrarchs.  Ancient Roman historians say he consulted seers and the last remaining Sibylline Book and had been assured (or thought so) of victory: an enemy of Rome would be defeated."  It didn't cross his mind that te enemy might be himself. 

Maxentius marched his men out to Saxa Rubra, ten miles north of Rome.  He placed his legions with their backs to the Tiber.  Modern tacticians say they were placed dangerously, too close to the River.  After preliminaries, including routing of Maxentus's cavalry on both flanks, Maxentius and his massive force began to retreat along the river toward Rome with Constantine's more experienced and better disciplned legions forcing them on from behind.

The end of the flight by Maxentius a his armies came at the "Milvian Bridge", but not the sturdy bridge that had crossed the Tiber before Maxentius had it taken down th keep Constantine from entering Rome.  Maxentius had construced next to the piers of the old Milvian a flimsier
wooden bridge or, by some accounts, a floating pontoon structure, designed perhaps for logistics, but never for the panic retreat of what had been a 100,000 man force, every man of whom wanted to get across safely and first.  The result was inevitable and is displayed in both images, above, of the collapse -- a contemporary frieze of the resulting watery massacre and Raphael's version, finally executed by Julio Romano in Raphael's Vatican Stanze. 

The drowned body of Maxentius was reportedly recovered from the Tiber, and his piked head was paraded through Rome to prove that the tyrant was dead.  And that may explain why he marched out of the stronghold, Rome.  He might really have feared the kind of trickery and treachery that let later enemies sac Rome without breaching Aurelian's walls.  He may well have known that he was disliked and thought of as a tyrant who had some likelyhood of betrayal.
Constantine was left in 312 AD in undisputed control of the western half of the Roman Empire, an Augustus, six years delayed from his York acclamation. 
Shortly thereafter, Constantine's Triumphal Arch (the one we see today, not a previous plastered wooden one) was completed in Rome to mark his victory over Maxentius, but, of course, it was not warranted:  you validly should get neither a triumph nor other triumphal honors for defeating another Roman.  But his arch was completed and inaugurated with remarkable speed -- by just looting monuments of previous victors. Many of the elements decorating the arch have been identified as elements of previous structures, and even the arch structure itself may have been started by someone else, perhaps even by Maxentius.

For More on the arch and whoever may have made which parts, see
https://en.wikipedia.org/wiki/Arch_of_Constantine



Also during his first few years as unchalenged Emperor in the west, Constantine undertook major building projects, as he had done in Trier.  For the most part, he was completing things started by Maxentius. 

The Basilica was the largest single structure ever built in the Roman forum and the last.  When Constantine took over the project, he shifted the main entrance away from the end opposite the semicircular apse and placed it on the long side facing into the forum.  Some scholars have proposed that Constantine's monumental statue of himself would have faced the doorway (facing toward the stairs), but most place it in the apse as shown in this image. 
Spolia on Constantine's triumphal arch.  The parts sculpted in his own time (not spolia) show how much sculptural ability had deteriorated by the early 4th Century.
 

Constantine's completion of the Basilica of Maxentius


This cut-away drawing of the Basilica shows the one side aisle
which is still standing.  The apse, nave, side aisle on the forum
siee and the stairway are gone. The one aisle that remains today
is still the largest structure in the forum.

The Edict of Milan
The Edict of Milan was a proclamation of religious tolerance issued jointly by Roman Emperors Licinius (east) and Constantine (west) in 313 AD.  (Licinius had gone to Milan to marry Constantine's younger half-sister, Flavia Julia Constantia.)  The Edict granted freedom of worship to ALL religions within the Roman Empire, effectively ending centuries of Christian persecution. It also required the return of confiscated properties to Christian communities and established a policy oc civic harmony by ensuring that all individuals, regardless of their faith, could practice their beliefs without state interference.

Unfortunately, at the Constantine convened and sponsored First Council of Nicaea (325 AD in what is now Iznik, Turkey) the assembled Christian leadership, bishops, etc., produced a "Nicene" creed that was considered rigidly dogmatic, and which effectively made heretics of large segments of Christianity. (It was specifically aimed, at the time, at granting power to persecute Arian Christians, but was widely used by Christians later to persecute other "heretic" Christians.)  When western "Roman Catholic" Christians later tried to introduce an extraneous phrase, filioque, into its Latin translation of the Nicene Creed, it caused the still ongoing schism between the "Catholic" and "Orthodox" Christian sects. 

Today's "Catholic" sect considers Nicaea to have been its first "ecumenical" council even though its avowed purpose and its result was expulsion of Arian Christians from the Communion on the basis of a doctrinal point. 

 -- Arians believed that Christ was created by the Father (Theos = Zeus) and, therefore, had a beginning, whereas the Council proclaimed that Christ "proceeds from" but always existed with the Father and the Holy Spirit.  Questionable logic.
  
The Edict of Milan was probably an
initiative of Constantine and, in its own wording, it clearly is aimed at reversing persecution of Christians.  Licinius is routinely ignored / forgotten in
discussions of the Edict.


The gender of the Holy Spirit was pointedly not specified in the Nicene Creed, which some scholars today say was a compromise: some believe today that in 325 AD there were still those that believed that she was "Hagia Sophia", a definitely female "Holy Wisdom".  Other scholars say that the whole question is irrelevant, and that God, whether Trinitarian or Nontrinitarian, is beyond biological sex or cultural gender.   The argument, however, is definitely, just interChristian.

Christianity is only 29% of the world's population but about 70% of the western world, and declining in both. The Roman Catholic sect is estimated at 17% of the world population, second only to Sunni Islam (now ca. 20%). 

 Islam believes in Allah and in Jesus as its second most great Rasoul (messenger/reformer, back to original Abrahamitic beliefs).  Mohamed is the greatest  Rasoul, with both being mistranslated as "Prophet", which implies the ability to "prophesy".  Islam is definitely not Trinitarian and uses the Arabic word "Tawhid" which denotes unity and therefore perfection to describe (they believe inadequately) Allah.  Tawhid is often translated as "Unitarian" which in Christianity is a Nontrinitarian "Protestant" sect.

[In three of the Gospels, Mathew, Mark, and Luke, Jesus, blindfolded in different circumstances, is mocked for not being able to "prophesy" who struck him.  All three stories are meant to emphasize translational misalignments between Jesus and his followers (Aramaic) and everyone else (Koine Greek).

The use of the word "sect" is anthopology terminology and not intended to be pejorative.

 While all of this was going on Constantine also took time (324 AD) to rehabilitate his mother, Helena, and to proclaim her an Augusta.  At some point she had become a Christian and had become an influence on Constantine in that direction.  She travelsed to Jerusalem and identified the place of the Crucifixion at the site where the Holy Sepulchre Church would be built at her initiative, and found and identified the True Cross in a cistern that is now below another part of the same church.  In the Holy Land Helna is said to have identified other early Christian sites.     
On returning to Rome, Helena is said to have identified sites that have, since then, been associated, as martyrions (burial sites), with Saints Peter and Paul.  Again, at her initiative, their major churches were there built.  The inscription on the "Red Wall" below the main altar that Marks the grave of Peter in "New" St. Peter's Basilica (really renaissance rather than new) is said to be from a time before Helena and may have induced her martyrion decision (in fact, quite possibly correctly).

Because of her conversion and Christian perspicacity (her site discoveries) Helena was sainted through popular devotion and tradition before the formal Canonization Congregation system existed.  She is recorded as having "pre-Congregation" Sainthood and is revered in Catholic , Orthodox, and Protestant cults.

At about the same time Constantine raised Helena's status to Augusta, he did the same for his wife Fausta, the daughter of Maximian and sister of Maxentius. The mystery of the ultimate cause of Fausta's murder ordered by Constantine a few years later (326) is still unsolved.

Master of all.  Costantine victor over Licinius, Augustus of the East

Chrysopolis (modern Uskudar, Turkey) was the scene of the decisive battle, on September 18, 324 AD, between the two Roman Augustae, Constantine of the West and Licinius of the East. 

The fact that you have probably never before heard of (or perhaps just didn't remember) Licinius, the other guy, is a big clue to who won.

Licinius had already suffered a naval defeat at the Battle of the Hellespont at the hand of Crispus Caesar, Constantine's son and presumptive heir, and had withdrawn his forces from Byzantion across the Bosphorus to Chalcedon in Bithnia.  Constantine followed and won the subsequent battle.  This meant Constantine was the only remaining emperor of Rome:  it ended the Tetrarchy.
In the naval battle (of the Hellespont), the smaller fleet of Crispus had outfought the fleet of Licinius commanded by Admiral Abantis opening the way for Constantine's newly built flotilla of light troop transports to cross and avoid a part of the Licinian army sitting on the Asian side of the Bosphorus at Lampascus that was tasked with stopping Constantine.

The main army of Licinius was assembled at Chalcedon and he called for the troops that were to have intercepted Constantine, and for some mercenary Visigothic auxiliaries to meet him there.  The army of Licinius was still depleted from an earlier defeat by Constantine at Adrianople (Thrace, July 3, 224 AD), and it is also not really clear if his reinforcements arrived in time.

Constantine troops disembarked up the coast at a place called the "Sacred  Promontory" and started to move south toward Chalcedon. Licinius marched a short distance north toward Chrysopolis, but Constantine arrived there first, and, after prayers, began the battle.  Both sides reportedly fought under the banners of their Gods, pagan or Christian. 		       

Location of the last battle, Chrysopolis.
Purple -- Constantine
Maroon -- Licinius

There was no subtlety involved.  Constantine's huge frontal attack led to the deaths of 25 to 30,000 of his opponents and the rest fleeing in a rout (reported by 5th century historian, Zosimus).  Licinius escaped and managed to gather 30,000 survivors at Nicomedia.

Licinius knew his 30,000 could not stand against Constantine's victors, and so, using his wife, Constantine's half-sister, as intermediary, Licinius negotiated with Constantine for mercy.  Initially Constantine spared his brother-in-law, but later, suspecting treachery, had Licinius killed (with encouragement from his Army).   A year later Constantine, had his nephew, the younger Licinius, the son of Licinius and his half-sister, had him killed as had been the father.  (It is because these two deaths that many people say that, although Constantine is thought of as a great benefactor of Christianity, Constantine has never been considered worthy of sainthood.)

Another year later Constantine ordered the deaths of Crispus Caesar, his own son and expected successor, and of his wife Fausta.

In 330 AD, Constantine inaugurated his new capital, Constantinopolis, built on the site of Greek Byzantion, and he ruled from there, leaving previous capitals, including Rome itself, destitute, because Constantine had brought all the previous imperial courts and bureaucracies (and their payrolls) to his new city.

For the next many years, until his death in 337 AD, Constantine was the sole surviving Tetrarch and, none were appointed in his wake.  His dynasty ruled until the death of Julian in 363.

Another reason Constantine is said to have been denied sainthood by organized christian sects is that he is thought to have "played the system" by, according to all accounts, declining baptism until he was on his death bed, at which time he could get get a completely clean slate -- all sin, they believe, is immediately and completely wiped away by baptism.  He would get into heaven, but no sect would acknowledge it by saying he was, to them, "saintly".