In 301 AD, Emperor Diocletian issued a reform that revaluated the Roman currency.
In 302 AD, Emperor Diocletian persecuted the Manichaeans, the new and most followed religion in Persia, accusing them of being a Persian fifth column (a group who undermine a larger group or a nation from within, usually in favor of an enemy group or another nation.)
In Persia, Narseh died and was succeeded by his son Hormizd II.
In 303 AD, (like in 33,) as part of the recovery of the Roman Empire, Emperor Diocletian continued with attacking other faiths and religions and launched the largest persecution of Christians in the history of the Empire. According to some historians, Caesar Galerius and Hierocles were said to have been the instigators. In a series of four edicts put out from early 303 AD to late 304 AD, Christians were now forbidden to worship in groups, were made to perform sacrifices according to Roman state religion (to Saturn,) and had to surrender any sacred texts. Churches were destroyed, and the clergy were all arrested. The persecution lasted until 313 AD, and thousands of Christians were killed. According to legends, among those put to death was Agnes of Rome, an alleged 12-year-old Christian girl who had refused marriage and instead consecrated her virginity to God. Hailed as a martyr, she was to be honored as the patron saint of chastity, gardeners, rape victims and virgins.
Also, Diocletian and Maximian met in Rome to celebrate the 20th anniversary of Diocletian’s accession, where it was said that the two emperors also agreed on a plan of abdication.
In 304 AD, Caesar Galerius was said to have won his fourth and final victory over the Carpi. Most of the surviving Carpi and Bastarnae were resettled in the Roman Empire, where they were split up.
In 305 AD, after suffering from some illness, Emperor Diocletian abdicated and retired to his palace at Salona (present-day Split) on the Adriatic coast. As planned, Maximian also retired from office, and settled in Southern Italy.
Constantius I and Galerius were declared Augusti; while Flavius Valerius Severus and Maximinus Daza were appointed Caesars.
In the summer, Constantius I and his troops made their way to Eboracum (York,) the capital of Britannia Secunda and home to a large military base. From there, they campaigned against the Picts, a people of North Britain known for their ‘Pictish stones’ with Viking-like symbols and the serpent. The name of ‘Pict’ was coined by the Romans, simply used to describe ‘non-Roman people of North Britain.’
Meanwhile, Maximinus Daza persecuted the Christians of Egypt, many of whom took refuge in the desert. In time, this refuge led to the monastic life (aka., monkhood.) In these monasteries, Coptic writing developed, supporting the propagation of Christian texts.
Before the end of the year, due to the Christian persecution and the monastic life, the Council of Illiberis decreed that priests must be celibate, which became the new tradition that has survived all through history – at least as a ‘image’ towards the people.
Within the Roman Empire, the elite families, who are now the only landowners, received the titles of senator and were exempted from the crushing taxes imposed on the rest of the population. However, by this time, the Senate had lost all its power and the landowners/senators did not attend any meetings of state affairs. Instead, the members of municipal senates were charged with the responsibility of collecting taxes and debts, while smaller landowners were held responsible for providing recruits for the Roman army, and with keeping wastelands under cultivation.
In 306 AD, Emperor Constantius I was killed in battle with the Picts and his son Constantine, was declared Caesar while Flavius Valerius Severus was elevated to emperor. Weeks later, Caesar Constantine instituted toleration of Christians in his territories.
Meanwhile, Caesar Galerius, introduced a poll tax to central and southern Italy and cut the size of the Praetorian Guard, with plans to disband the Guard altogether. This action leads to a revolt led by Maxentius, son of former Western Emperor Maximian, the Praetorian Guard and members of the Senate in Rome.
Southern Italy supported Maxentius revolt, as did Africa, Corsica, Sardinia and Sicily. Maxentius recalled his father Maximian from retirement, and proclaimed himself Emperor.
In Britain, due to Constantine, Christianity slowly began to get a foothold.
In 307 AD, Galerius sent Valerius Severus to suppress the rebellion in Rome. However, faced with their former emperor Maximian, the soldiers deserted him and Severus was taken hostage by Maxentius.
During late summer, Galerius made an attempt to besiege Rome, but it did not sit well with his troops and he retreated back to northern Italy as he feared being trapped. As Galerius retreated with his army, Maxentius executed Severus.
Meanwhile, Maximian had travelled to Caesar Constantine in Gaul and had made a deal in which Constantine would marry Maximian’s younger daughter Fausta and be elevated to Augustan rank in Maxentius’ secessionist regime.
In 308 AD, old Maximian returned to Rome but soon fell out with his son, being displeased by Maxentius ruling and how the government had been weakened.
Maximian expected the soldiers to side with him, but they sided with Maxentius, and Maximian was forced to leave Italy in disgrace.
In the winter, Caesar Galerius recalled former Emperor Diocletian briefly from retirement, and they convened with Maximian. Diocletian persuaded Maximian to return to retirement, and he and Galerius declared Maxentius a public enemy.
Meanwhile in Rome, Maxentius presented himself as the ‘Conservator Urbis Suae’ (Preserver of His Own City.) He began the construction of ‘Basilica of Maxentius’ (or Basilica Nova,) the largest building in the Roman Forum. He also instituted tolerance of Christians in his territories.
In 310 AD, after successfully quelling rebellions in Africa, Caesar Maximinus Daza was proclaimed Augustus by his troops. Galerius felt forced to recognize him as co-ruler of the East. The Roman Empire was thus divided between seven simultaneous emperors: Galerius (East,) Maximinus Daza II (East,) Licinius (Middle,) Constantine I (West,) Maximian (West,) Maxentius (Italy,) and Domitius Alexander (Africa.)
However, tension had risen between Maximian and Constantine, and Maximian tried to bribe Constantine’s troops. Maximian was captured, reproved for his crimes, and stripped of his title for the third and last time. Constantine granted Maximian some clemency but strongly encouraged his suicide. In July 310 AD, Maximian hanged himself.
Also, Constantine ordered the minting of a new coin, the solidus, in an effort to offset the declining value of the denarius and bring stability to the imperial currency by restoring a gold standard. The solidus (later known as the bezant) was minted in the Byzantine Empire without change in weight or purity until the 10th century.
In 311 AD, while being ridden with sickness, Emperor Galerius declared on his deathbed religious freedom, and issued his Edict of Serdica, ending the Diocletianic Persecution of Christians in the Eastern part of the Roman Empire.
After Galerius’ death, Maximinus Daza and Licinius divided the Eastern Empire between themselves. Also, Daza resumed the persecution of Christians within his borders.
In 312 AD, Constantine I crossed the Cottian Alps with an army of roughly 40,000 men and fought Maxentius in four battles, the last being the ‘Battle of the Milvian Bridge,’ where Maxentius was defeated. Constantine thus became the only Roman emperor in the West. According to legends, prior to the battle, Constantine allegedly had a vision of a cross (labarum) with the phrase “in hoc signo vinces” (In this sign you shall conquer.) This encouraged him to convert to Christianity. Constantine adopted this phrase as a motto, and had the letters X and P (the first letters of the Greek word Christ) emblazoned on the shields of his soldiers.
As Constantine entered Rome, he staged a grand adventus in the city, and was met with popular jubilation. Maxentius’ body was fished out of the Tiber and decapitated.
Constantine then went on and forged an alliance with co-emperor Licinius, and offered him his half-sister, Constantia, in marriage. The Praetorian Guard and the Imperial Horse Guard were disbanded.
In 313 AD, the retired Emperor Diocletian died in his palace in Split. Meanwhile, Emperors Constantine I and Licinius convened in Mediolanum (Milan,) where they issued the Edict of Milan. This edict ended the Great Persecution against the Christians and was the first legislation in western history to decree freedom of religion.
Licinius then proceeded to attack his rival Maximinus in Thrace, forcing him to commit suicide. Afterwards, he continued to purge the wider Tetrarchic dynasty. He executed Galerius’ son Candidianus, Valerius Severus’ son Severianus, and Maximinus’ wife, son and daughter.
In 315 AD, Constantine, now called ‘Constantine the Great,’ together with his co-emperor Licinius battled the Sarmates, the Goths and the Carpians along the Danube. The Arch of Constantine was completed near the Colosseum at Rome to commemorate Constantine’s victory over Maxentius. Also, Crucifixion was abolished as punishment in the Roman Empire.
It is also said, that during this period the lamb became the symbol of Jesus in Christian art.
In 316 AD, Constantine proposed Bassianus as Caesar and to give him power over Italy. Licinius refused, and had Bassianus executed for conspiracy. He then elevated Valerius Valens to Augustus, and mobilized an army against Constantine. Months later, in October, Constantine defeated Licinius at what was known as the ‘Battle of Cibalae.’ Licinius was forced to flee to Sirmium and lost all of the Balkans except for Thrace.
In December, Constantine caught up with Licinius in Bulgaria, and had him and Valerius Valens forced to surrender.
In 317 AD, after being defeated, Licinius reconciled with Constantine, had him recognized as senior Emperor, and had Valerius Valens executed.
In 318 AD, Emperor Constantine the Great gave the ancient Roman town Drepana (Asia Minor) the name Helenopolis, after his mother Helena, and built a church in honor of the martyr St. Lucian.
In 319 AD, Christianity is introduced in Colchis, present-day Georgia.
In 320 AD, Crispus, the eldest son of Emperor Constantine, lead a victorious campaign against the Franks, assuring twenty years of peace along the Rhine frontier. Also, the fake date of December 25 was introduced as the birthday of Jesus.
Meanwhile, Licinius backed out on the religious freedom promised by the Edict of Milan, and began a new persecution of Christians in the Eastern Roman Empire. He imprisoned Christians, confiscated their properties and destroyed churches.