In 308 Diocletian emerged from retirement to support Galerius and together the two met with Maximian at Carnuntum in November. Under the watch of Diocletian and Maximian, Galerius promoted his officer Licinius to become the new western Augustus, and confirmed Maximinus Daza and Constantine as Caesars. With the empire thus ‘stabilized’, Diocletian returned to his palace and cabbages at Salonae, while Maximian retired to Gaul.in wikipedia
In c.309 Hormizd II of Persia led an army into Syria to demand tribute from the Ghassanids, who appealed to Rome for support. The Persians then killed the Ghassanid king, but later suffered a major setback when Hormizd himself was ambushed and fatally wounded while hunting in the desert. Taking advantage of this situation to gain influence within the empire, the Persian nobility and Zoroastrian clergy murdered Hormizd’s son and successor Adur Narseh, leaving the latter’s infant brother Shapur II as shah. Meanwhile, the Ghassanids, possibly with some Roman assistance, raided into Mesopotamia and plundered the outskirts of Ctesiphon.in wikipedia
Shortly after the death of his father Maximian, Maxentius sent several cohorts under the command of his praetorian prefect Rufius Volusianus to Africa, where the usurper Domitius Alexander was claiming to be co-emperor with Constantine. Volusianus easily defeated Alexander, who took refuge behind the walls of Cirta, only to be captured and later executed by strangulation. In reprisal for supporting Alexander, Maxentius had the government of Africa purged, the capital Carthage plundered and burned, and Cirta destroyed (three years later it would be rebuilt by Constantine as the city of Constantine).in wikipedia
In 309 the courtiers and clergy of Sasanian Persia had crowned the very young Shapur II as shah—according to legend the crown had been placed on the womb of his pregnant mother 40 days before his birth—in the hope of molding him as a puppet. However, this regency proved ineffective and was unable to prevent the Arab tribes of the Gulf region from throwing off Persian rule. By the 320s the emboldened Arabs were raiding southern Mesopotamia and across the Gulf into the traditional Persian heartland of Pars, facing no meaningful military response from the Persian regime.in wikipedia
Some time between 395 and 320 the Lakhmid king Imru al-Qays ibn Amr seems to have achieved leadership over the Arab tribes of the western Persian Gulf and subjugated the polity of Ma‘ad in central Arabia to form the “Kingdom of All Arabs”. From here he waged war against his erstwhile overlords the Sasanian Persians, but was eventually defeated by Shapur II at Al-Hirah, the Lakhmid capital, in 325. After this Imru al-Qays eventually fled to Roman territory, where he died near Namara, Syria, in 328.in wikipedia
In early May 311 Galerius died of illness and was interred at his palace at Felix Romuliana (Gamzigrad, Serbia) by Licinius. In accordance with what appear to have been the late emperor’s wishes, Maximinus Daza, longest-serving of the three remaining tetrarchs and father-in-law of Galerius’ son Candidianus, became the senior Augustus and took control of the dioceses of Asiana and Pontica. Stability seems to have been preserved until at least early 312—when Maximinus named Constantine and Licinius as consuls—but no new tetrarch was appointed to bring the total number back to four.in wikipedia
In October 312 Constantine marched down the Via Flaminia towards Rome where Maxentius, concerned by dissent in the city and encouraged by omens that he would not fall on the day of his accession (28 October), assembled in front of the Milvian Bridge to oppose him. Constantine, who had his own omens, by now had his soldiers adorn their shields with combined Greek letters (either chi and rho or chi and tau) that would later become symbols of imperial Christianity. When Constantine prevailed, Maxentius and his forces fled across a pontoon bridge—constructed to facilitate their movement across the Tiber—only to have it collapse and send many, including the usurper himself, to drown in the river. The following day Constantine entered Rome; he was now supreme ruler of the western Roman Empire.in wikipedia
