Ala Gallorum Petriana

The nominal strength of the ala was 720 men, consisting of 24 turmae each with 30 horsemen.

[2] It is listed on military diplomas for the years 98 to 135 AD.

At an uncertain time (possibly under Quintus Petillius Cerialis at 71/74), the Ala was transferred to the province of Britannia, where its presence is first attested by a military diploma dated to 98.

[3] Other diplomas dated from 122 to 135 attest the unit remained in Britannia.

It was under the direction of a prefectus, who was subordinate the Dux Britanniarum.

Fragment of inscription honoring one of the Prefects of the Ala Gallorum Petriana, found in Carlisle ( CIL VII.929 )