ORDER OF BATTLE // -85 BCE
Battle of Orchomenus
Estimated force strength by side, with confidence labels per surviving record.
Forces engaged
2 sides catalogued · combined 105,000–110,000 estimated
Roman Republic
30,000
Medium-confidence figure
Pontus
75,000–80,000
Medium-confidence figure
Battle context
The Battle of Orchomenus was the decisive engagement that ended the Mithridatic invasion of Europe during the First Mithridatic War. Fought in autumn 86 BCE, it saw Sulla's Roman force of roughly 30,000 defeat a Pontic army under Archelaus numbering between 75,000 and 80,000, with Pontic casualties recorded at 15,000. The scale of the defeat was severe enough that Archelaus subsequently defected to Rome. Together with its outcome, the battle effectively expelled Pontic forces from the European theater and foreclosed Mithridates VI's ambitions on that front, setting the conditions for the eventual peace that concluded the First Mithridatic War in 84 BCE.
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