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Theodosius marries Galla, sister of Valentinian II, tying eastern and western houses before the war with Maximus

Handbook chronology places the marriage in 387 as Theodosius prepared to intervene against Magnus Maximus on Valentinian II’s behalf. This is dynastic cohesion, not the 388 killing of Maximus. In the causal graph this event strengthens Social Cohesion, a driver that strengthens Having a say in government — an improving welfare path.

Sources: [1][2]

Read the full account

The dated heading is that marriage-alliance, not a unique peace index.

Context

A marriage that binds two imperial courts is a cohesion path. Civil-war costs stay on 388.

Theodosius I’s documented role is bounded by other offices and collaborators named in the sources below.

Handbook chronology places the marriage in 387 as Theodosius prepared to intervene against Magnus Maximus on Valentinian II’s behalf. Aelia Flaccilla had died. This is dynastic cohesion, not the 388 killing of Maximus.

Why it matters

The 387 marriage is a cohesion path of high confidence in the standard file.

Who was responsible

Contribution type and responsibility level for each recorded actor — not sole-author shorthand.

  • Theodosius I

    Person

    Direct responsibility

    responsibility level 0.4 · verified

What changed

Fact → Driver → Indicator. Relationship strength orders the paths; it is not the observed indicator movement.

    1. FactTheodosius marries Galla, sister of Valentinian II, tying eastern and western houses before the war with Maximus
    2. strengthensDriverSocial Cohesion
    3. strengthensIndicators (2)Having a say in government
    Improving path

    impact weight 0.5 · Effect from 1 January 387 · verified

    The 387 marriage is a cohesion path of high confidence in the standard file.

    • Having a say in government

      via Social Cohesion

      Better

      Strengthens · Relationship strength 0.23 (weight 0.5 × strength 0.45)

      Observed

      29.8% of population aged 16-65 years · 8.13 below the normal line (2023)

      Worse than normal

      Two readings: 30.2% of population aged 16-65 years (2021) and 29.8% of population aged 16-65 years (2023).

      20212023

      Above normal = better

    • Rule of Law Gap from the Highest Governance Score

      via Social Cohesion

      Better

      Weakens · Relationship strength 0.23 (weight 0.5 × strength 0.45)

      Observed

      43.9 Score · 43.9 above the normal line (2024)

      Worse than normal

      26 readings, 1996–2024: rose from 43 Score to 43.9 Score.

      Normal is zero · any amount = worse

Evidence

The sources behind this fact and its verification state.

Verified2 sources on file
  1. 1.De Imperatoribus Romanis — Theodosius ILoyola University Chicago · High credibility · verified
  2. 2.Britannica — Theodosius IEncyclopaedia Britannica · High credibility · verified
What the sources establish

Britannica and DIR independently narrate the western crisis of Maximus and Theodosius’s intervention for Valentinian II, in which the Galla marriage is the received dynastic instrument.

Theodosius I did not file a later UNESCO form, a later Loeb colophon, or a later museum label as a personal act.

Causal path

How this event connects to drivers and indicators in the graph.

  1. ActorTheodosius I
  2. contributed toFactTheodosius marries Galla, sister of Valentinian II, tying eastern and western houses before the war with Maximus
  3. strengthensDriverSocial Cohesion
  4. strengthensIndicatorHaving a say in government

Cite this page

Factrail. (2026). Theodosius marries Galla, sister of Valentinian II, tying eastern and western houses before the war with Maximus. Factrail. https://factrail.ai/facts/theo-galla-marriage-387

https://factrail.ai/facts/theo-galla-marriage-387

Accessed 16 October 2026.

By the · Method: how we source and score · Last reviewed

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