Legio XXII Deiotariana

Legio vigesima secunda Deiotariana ("Deiotarus' Twenty-Second Legion") was a legion of the Imperial Roman army, founded ca. 48 BC and disbanded during the Bar Kokhba revolt of 132–135. Its cognomen comes from Deiotarus, a Celtic king of Galatia. Its emblem is unknown.

The legion was levied by Deiotarus, king of the Celtic tribe of the Tolistobogii, who lived in Galatia, modern Turkey. Deiotarus became an ally of the Roman Republic's general Pompey in 63 BC, who named him king of all the Celtic tribes of Asia minor, which were collectively known as Galatians (hence the name Galatia for the region). Deiotarus levied an army and trained it with Roman help; the army, in 48 BC, was composed of 12,000 infantrymen and 2,000 horsemen. Cicero writes that the army was divided into thirty cohortes, which were roughly equivalent to three Roman legions of the time. This army supported the Romans in their wars against king Mithridates VI of Pontus, and contributed to Roman victory in the Third Mithridatic War.

After a heavy defeat against king Pharnaces II of Pontus near Nicopolis, the surviving soldiers of Deiotarius army formed a single legion, which marched besides Julius Caesar during his victorious campaign against Pontus, and fought with him in the battle of Zela (47 BC).

When the Roman Empire integrated the Galatian kingdom, this legion, which had been trained by the Romans and had fought under Roman commanders, became part of the Roman army; since Caesar Augustus had already 21 legions, the legion received the number XXII.

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