a cohort: a unit of the Roman army, several hundred soldiers serving under one commander
Every appearance of this word in the New Testament is military, and Roman. In older Greek it meant something coiled or wound, a rope's coil, and by the first century it had become the ordinary Greek term for what the Romans called a cohort: one tenth of a legion, in principle four to six hundred men, under an officer the New Testament calls a commander of a thousand. Judea was occupied territory, so such units were part of ordinary life, quartered at Caesarea and in the fortress that overlooked the temple courts in Jerusalem.
The word does two jobs. Sometimes it names the unit as an institution, the formation a man belongs to and an officer is in charge of: Cornelius is a centurion of the Italian cohort, Paul is handed over to a centurion of the Augustan cohort, and the officer who pulls Paul out of the riot is the commander of the Jerusalem unit. Sometimes it names the soldiers themselves, present and acting together: the troops who crowd around Jesus in the governor's headquarters, and the armed party that goes out with Judas at night.
Size is what English readers most often get wrong. When Matthew and Mark say the soldiers called together the whole company, most scholars take that to mean the men on duty rather than a parade of six hundred, and units in the field were rarely at their full paper strength anyway. What the word carries is not a headcount but organization: men under orders, under one command, belonging to the occupying power.
The neighboring Greek words divide the field cleanly:
- λεγεών is the whole legion, about ten times larger, and in the Gospels it becomes an image of overwhelming numbers.
- στράτευμα is troops or an army in general, with no fixed size and no fixed place in a chain of command.
- παρεμβολή is the barracks or camp where such soldiers were quartered, naming the place rather than the body of men.
Nuances
Whether σπεῖρα in John 18:3 (and 18:12) denotes an actual detachment of Roman auxiliary troops from the Antonia garrison taking part in the arrest of Jesus, or whether the Fourth Evangelist applies the technical military term loosely to the Jewish temple police, who are the only arresting party in the Synoptic accounts.
- majorityThe term keeps its normal technical sense: a Roman detachment accompanied the temple officers, which is why a tribune is named alongside them in 18:12. Roman cooperation in a night arrest at the request of the chief priests is historically plausible given the Antonia garrison's proximity to the temple.; BDAG, s.v. σπεῖρα; R. E. Brown, The Gospel According to John XIII-XXI, Anchor Bible 29A (New York: Doubleday, 1970), ad loc.
- minorityThe term is used loosely of the Jewish force, since the Synoptic tradition knows nothing of Roman involvement before Jesus is delivered to Pilate, and the Fourth Gospel's interest is in presenting the world as a whole arrayed against Jesus.; C. K. Barrett, The Gospel According to St John, 2nd ed. (Philadelphia: Westminster, 1978), ad loc.