COHORT cō’ hôrt (σπει̂ρα, G5061, company, band). KJV “band.” In the RSV alternately “battalion” (Matt 27:27; Mark 15:16) and “band” (John 18:3, 12). Nominally the tenth part of a Rom. legion, or 600 men.
The traditional Rom. legion of 6,000 men was divided into ten cohorts. Each of these was divided for administrative purposes into three maniples and six centuries. In the minor provinces, e.g., Judea, Rom. troops were usually recruited locally and assigned to auxiliary cohorts which were posted alone in frontier forts and in places of unrest. The auxiliary cohort numbered from 500 to 1,000 men and was composed of infantry and cavalry. They were commanded by prefects or tribunes. Χιλίαρχος (commander of 1,000) is tr. in the KJV as “captain” or “chief captain” and in the RSV “tribune.”
The Italian Cohort (Acts 10:1), of which Cornelius was a centurion, commander of 100, was prob. composed of Rom. citizens. It has been identified with the cohors II Italica which is known to have been in Syria in a.d. 88 (CIL XVI. 35).
In the NT the cohort often functioned as garrison troops and as local military police (Matt 27:27; John 18:3).
International Standard Bible Encyclopedia (1915)
Augustan Cohort (band)
AUGUSTAN COHORT (BAND). (Gr. σπει̂ρα, G5061). This title which occurs in Acts 27:1 has occasioned much speculation. A cohort was normally a tenth part of a legion and was itself divided into six centuries, each under a centurion. A cohort, therefore, comprised 600 men. In the auxiliary troops the cohorts were the basic unit of division and each numbered 500 or 1,000 men. Each bore some honorific title such as Gallica or fidelis, and they were commanded by prefects or tribunes.
The Gr. word in the present context is speira which normally tr. the Lat. manipulus, a force of two cohorts (e.g. Polybius, XI, 23. 1), although at Acts 10:1, as in Josephus, War IV. iv. 2, it seems to be used for cohort. None of these usages, all of which contain a measure of uncertainty, relieves the difficulty of the present context. If the “ ” was a true cohort, regular or auxiliary, why was it commanded by a centurion?
Ramsay, following the great Ger. scholar Mommsen, supposes that the unit was a name for a special corps of imperial couriers called frumentarii, functioning as liaison officers between the emperor and his armed forces (W. M. Ramsay, Saint Paul the Traveller and Roman Citizen, 315, and R. J. Knowling, EGT Acts, 516, 517). On such an assumption, Julius would be a legionary centurion detailed for this special task. This, however, does no more than account for the fact that it was a centurion who commanded this detachment. Was he, or the whole bodyguard, called Augustan?
The only contribution which can be made to this question is, first, the fact that there is archeological evidence for a Cohors Augusta I in Syria in the time of Augustus (Dessau, ILS 2683). Secondly, it may be mentioned that Josephus wrote of a turma or cavalry called “Sebastan,” that is “Augustan,” the Gr. word in the present context. Sebaste was Samaria, refounded by Herod I under that name in honor of Augustus. There the problem must be left. Julius may have been a praetorian sent on a special mission to Caesarea.