AD 313

Licinius

Milan conference and marriage alliance of Constantine and Licinius

Licinius married Constantine’s half-sister at Milan while Maximinus Daia was preparing to invade his eastern territory.

A summit under pressure

Constantine and Licinius met at Mediolanum in February 313 and negotiated political arrangements while Maximinus Daia threatened Licinius’s position in the east. The month is well supported; no exact day is securely recoverable.

Licinius married Constantine’s half-sister Constantia, formally sealing their dynastic alliance. Maximinus’s impending invasion is what made the settlement urgent for Licinius.

What Licinius agreed to carry east

The emperors agreed on a policy permitting Christians and others to choose their religion freely, and providing for the restoration of Christian corporate property. For Licinius the practical commitment was to extend into his own territories the freedom of worship and restitution already in force in Constantine’s West.

Nothing signed at the February meeting survives. The policy known retrospectively as the Edict of Milan is preserved through later implementing texts, and normal Roman practice could require each emperor to promulgate it separately in his own jurisdiction.

Where each emperor went next

The emperors separated after the marriage. Constantine returned toward his western territories; Licinius moved east to fight Maximinus, who still controlled eastern territory while the conference was taking place.

Only after that victory did Licinius publish the surviving religious-policy letter, at Nicomedia on 13 June 313. The alliance sealed at Milan later collapsed into civil war between the two men.

Sources

Researched 23 Aug 2026 5 sources 2 audit passes, 2 issues open Date disputed

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

Date disputed. Sources disagree; the research places it at ~0313-02.

What the sources leave uncertain

February 313 is well supported, but no exact day is securely recoverable.
Whether the conference produced a formal edict, a policy memorandum or simply an agreement later implemented through separate enactments remains disputed.
The universal language survives in Licinius’s eastern implementing letter; normal Roman practice could require each emperor to promulgate policy separately in his own jurisdiction.