Battle of Issus (194) — the same event in Cassius Dio and Herodian, History of the Empire

Cassius Dio: A great battle at Issus near the Cilician Gates: Niger's army had the advantage, but a storm struck their faces and Valerianus attacked…

What each source says

Cassius Dio, Roman History · AD 194 · Issus

A great battle at Issus near the Cilician Gates: Niger's army had the advantage, but a storm struck their faces and Valerianus attacked from behind, putting them to flight

In this struggle Valerianus and Anullinus commanded the army of Severus, while Niger himself was present with his own forces and arrayed them for the battle.
Location: 75(74).7.1

Cassius Dio, Roman History · AD 194 · Issus

This battle was the war's worst disaster; 20,000 of Niger's men fell

This proved to be the greatest disaster of the war; for twenty thousand of Niger's followers perished.
Location: 75(74).8.1

Herodian, History of the Empire · AD 194 · Issus

Niger fights on the plain of Issus with a large army made up mostly of recruits, but is badly defeated and flees.

Niger, being mounted on a generous Steed, fled with a few Followers to Antioch whet he found the Remainder of the People deferring the whole City fill’d the PI…
Location: 3.4

Place: Issos

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