Constantius Chlorus' Campaign Against Carausius and the Rise of Allectus (293 CE)

In 293 CE, Constantius Chlorus, newly appointed Caesar of the West under Emperor Diocletian’s Tetrarchy, was tasked with reclaiming Britain and northern Gaul from the usurper Marcus Aurelius Carausius. Carausius, a Menapian naval officer, had seized power in 286 CE, declaring himself Augustus and establishing an independent Britannic Empire.

1. The Fall of Gesoriacum (Bononia) and the Defeat of the Franks

• Constantius launched a campaign to isolate Carausius by attacking his mainland holdings.
• He successfully recaptured Gesoriacum (modern Boulogne, France), the key Roman naval base on the English Channel.
• To ensure a secure rear before invading Britain, he also defeated Carausius’ Frankish allies in Batavia, further cutting off continental support for the breakaway state.

2. The Assassination of Carausius and the Rise of Allectus

• The loss of Gaul and its ports weakened Carausius' position, reducing his ability to control trade and reinforce Britain.
• Sensing his vulnerability, his finance minister, Allectus, assassinated him in 293 CE and seized power.
• Allectus ruled Britain independently for three years, but his reign was not marked by open conflict with Rome, leading to a temporary period of peace.

3. Rome’s Next Move: Preparing for the Final Invasion

• Though the recapture of Bononia was a major victory, the Britannic Empire still controlled Britain and its defenses.
• Constantius could not immediately launch an invasion, as he needed time to build a new fleet and prepare a coordinated offensive.
• Over the next three years (293–296 CE), the Romans rebuilt their naval capabilities, setting the stage for the final reconquest of Britain in 296 CE.

4. Significance of the Conflict

• The fall of Gesoriacum marked the beginning of the end for the Britannic Empire, as it isolated Allectus’ regime from the continent.
• The assassination of Carausius demonstrated internal instability within the breakaway government.
• Although Allectus ruled peacefully for a time, he was ultimately unable to stop the Roman reconquest, which would come in 296 CE under Constantius Chlorus.

Conclusion: The Beginning of the End for the Britannic Empire

While Constantius’ victories on the continent weakened the secessionist state, the Britannic Empire under Allectus endured for three more years. However, Rome’s preparations for invasion were underway, ensuring that Britain would soon return to imperial control.