** Battle of Lingones — Caesar Constantius Chlorus defeats the Alemanni

Soon after his father's death Constantius is supposed to have ordered a massacre of his relatives descended from the second marriage of his paternal grandfather Constantius Chlorus, though the details are unclear.

In 293, Constantius Chlorus launched a second offensive, besieging the rebel's port at Boulogne and cutting it off from naval assistance.

Constantius Chlorus returned in 306, aiming to invade northern Britain.

His paternal grandparents were Western Roman Emperor Constantius Chlorus and his second wife, Flavia Maximiana Theodora.

Constantius II ordered the murders of many descendants from the second marriage of Constantius Chlorus and Theodora, leaving only Constantius and his brothers Constantine II and Constans I, and their cousins, Julian and Gallus ( Julian's half-brother ), as the surviving males related to Emperor Constantine.

* 293 – Roman Emperors Diocletian and Maximian appoint Constantius Chlorus as Caesar to Maximian.

* 250 – Constantius Chlorus, Roman Emperor ( d. 306 )

In 293, feeling more focus was needed on both civic and military problems, Diocletian, with Maximian's consent, expanded the imperial college by appointing two Caesars ( one responsible to each Augustus ) — Galerius and Constantius Chlorus.

* Augusta Treverorum ( modern Trier, in Germany ) was the capital of Constantius Chlorus, the western Caesar, near the strategic Rhine border, it had been the capital of Gallic emperor Tetricus I ; this quarter became the prefecture Galliae.

Their Caesares, Galerius and Constantius Chlorus, were both raised to the rank of Augustus, and two new Caesares were appointed: Maximinus ( Caesar to Galerius ) and Flavius Valerius Severus ( Caesar to Constantius ).

:: Gallia et Hispaniae Constantius Chlorus ( 293 – 305 )

:: Gallia, Hispaniae et Britannia Constantius Chlorus ( 305 – 306 )

The first book sketches briefly the history of the early Roman emperors from Augustus to Diocletian ( 305 ); the second, third and fourth deal more fully with the period from the accession of Constantius Chlorus and Galerius to the death of Theodosius I ; the fifth and sixth, the most useful for historians, cover the period between 395 and 410, when Priscus Attalus was deposed ; for this period, he is the most important surviving non-ecclesiastical source.

* Constantius Chlorus and Galerius are declared Augusti ; Flavius Valerius Severus and Maximinus II Daia are appointed Caesars.

Constantius Chlorus requests leave for his son Constantine I who remains at Galerius's court in Nicomedia, as a virtual hostage.

* Battle of Lingones: Constantius Chlorus defeats the Alamanni in the territory of the Lingones ( Langres ) in Gaul.

* Constantius Chlorus defeats the Alemanni and fortifies the town of Konstanz ( Germany ).

Medal of Constantius Chlorus capturing Roman London | Londinium ( 296 )

* Constantius Chlorus assembles two invasion fleets with the intent of crossing the English Channel.

* Constantius Chlorus reconquers Britain, he rebuilds the cities Eboracum ( York ), Londinium ( London ), and Verulamium ( St Albans ).

Flavius Claudius Julianus, born in May or June 332 or 331 in Constantinople, was the son of Julius Constantius ( consul in 335 ), half brother of Emperor Constantine I, and his second wife, Basilina, a woman of Greek origin.

His mother was an Arian, sister of Clearchus, also an Arian, and a paternal granddaughter of Gallus ( born c. 370 ), son of Anastasia ( born c. 352 ) and husband, in turn daughter of Flavius Claudius Constantius Gallus and wife and cousin Constantina.

* 421 – Galla Placidia, wife of the Emperor Constantius III, becomes a widow for the second time when he dies suddenly of an illness.

* September 2 – Constantius III dies suddenly of an illness, his wife Galla Placidia becomes for the second time a widow.

To strengthen the ties between the emperor and his powerful military servant, in 289 Constantius divorced his wife ( or concubine ) Helena, and married the emperor Maximian ’ s daughter, Theodora.

Theodora, the wife of Constantius Chlorus, is often called Maximian's stepdaughter by ancient sources, leading to claims by Otto Seeck and Ernest Stein that she was born from an earlier marriage between Eutropia and Afranius Hannibalianus .< ref > Aurelius Victor, de Caesaribus 39. 25 ; Eutropius, Breviaria 9. 22 ; Jerome, Chronicle 225 < sup > g </ sup >; Epitome de Caesaribus 39. 2, 40. 12, quoted in Barnes, New Empire, 33 ; Barnes, New Empire, 33 .</ ref > Barnes challenges this view, saying that all " stepdaughter " sources derive their information from the partially unreliable work of history Kaisergeschichte, while other, more reliable sources, refer to her as Maximian's natural daughter .< ref > Origo Constantini 2 ; Philostorgius, Historia Ecclesiastica 2. 16 < sup > a </ sup >, quoted in Barnes, New Empire, 33.

The sources are equivocal on the point, sometimes calling Helena Constantius ' " wife ", and sometimes, following the dismissive propaganda of Constantine's rival Maxentius, calling her his " concubine ".

In order to obtain a wife more consonant with his rising status, Constantius divorced Helena some time before 289, when he married Theodora, Maximian's daughter.

* Flavia Maximiana Theodora, daughter of the Roman Emperor Maximian and second wife of the Emperor Constantius I Chlorus.

In 293, Theodora married Flavius Valerius Julius Constantius ( later known as Constantius Chlorus ), after he had divorced from his first wife, Helena, to strengthen his political position.

* Faustina ( empress ), wife of Constantius II

Gallus was a son of Julius Constantius by his first wife Galla.

Gallus ' paternal grandparents were the Western Roman Emperor Constantius Chlorus and his second wife Flavia Maximiana Theodora.

Gallus had three siblings: an elder sister, of unknown name, who was the first wife of Constantius II, an elder brother, also of unknown name, who died in the purges after the death of Constantine I, and a younger half-brother by his father's second marriage, named Flavius Claudius Iulianus, commonly known as Julian.

* Flavia Maxima Constantia, daughter of Constantius II and his third wife Faustina

* Galla ( wife of Julius Constantius )

Galerius's sister gave birth to a son, Maximinus Daia, and Galerius's daughter by his first wife, Valeria Maximilla, married Maxentius, son of Maximian by his wife Eutropia ; Eutropia's first marriage ( to Afranius Hannibalianus ) had produced a daughter, Theodora, who became the second wife of Constantius Chlorus (" the Pale ") in 289 ( adopted by Maximian on March 1, 293 ).

Constantius I " Chlorus " married twice ; his first wife St. Helena bore him a son, Constantine I whose second wife Fausta ( daughter of Maximian and Eutropia ; sister of Maxentius ; half-sister of Constantius I's second wife Theodora ) bore him three sons ( Constantine II, Constantius II, and Constans I ) and two daughters ( Constantia and Helena ); these children were nieces and nephews of Maxentius, half-nieces and half-nephews of Licinius ( who had married their father's half-sister ), and grandchildren of Maximian.

A few days later, Julian was married to Helena, the last surviving sister of Constantius.

In 355, Julian was summoned to appear before the emperor in Mediolanum and on 6 November was made Caesar of the West, marrying Constantius ' sister, Helena.

He takes command of the western provinces and marries Constantius ' sister, Helena.

Constantius was either married to, or was in concubinage with, Helena, who was probably from Nicomedia in Asia Minor.

Constantius married Coel's daughter Helena and became king of Britain.

The identification of Helena as British had previously been made by Henry of Huntingdon, but has no historical validity: Constantius had divorced Helena before he went to Britain.

The precise legal nature of the relationship between Helena and Constantius is also unknown.

Some scholars, such as the historian Jan Drijvers, assert that Constantius and Helena were joined in a common-law marriage, a cohabitation recognized in fact but not in law.

Others, like Timothy Barnes, assert that Constantius and Helena were joined in an official marriage, on the grounds that the sources claiming an official marriage are more reliable.

In the legend Helena, the daughter of Cole, married the Roman senator Constantius Chlorus, who had been sent by Rome as an ambassador and was named as Cole's successor.

Constantius married Coel's daughter, Helena, and crowned himself as Coel's successor.

According to Socrates, after Constantine was proclaimed Caesar then Emperor, he ordered that all honor be paid to his mother, Helena to make up for the neglect paid her by her former husband, Constantius Chlorus.