Centurion was a class of officer within a Roman Legion who commanded a unit called a century. By New Testament times a century was eighty men. They might be assigned command of other units. In Acts 23:23 two Centurions commanded a force of four hundred seventy troops.
There were sixty Centurions within a legion in a hierarchy where the most junior one commanded a single century and the most senior one commanding all of the centuries. The most junior Centurion earned seventeen times as much as a common soldier and the most senior Centurion earned four times that. The most senior Centurion possessed Equestrian rank, the next rank below Senator. Pontius Pilate was of Equestrian Rank.
Centurions were normally drawn from units of men with sixteen years of experience or more. Of these the best of the best were chosen to be Centurions.
The Centurion who said to Jesus “I am not worthy to for you to come under my roof,…” Mathew 8 and Luke 7 was a man who understood power. He saw power in Jesus.
The Army of the Ceasars by Michael Grant, Scribners, New York, 1974
The Roman Empire by Chester Star, Oxford University Press, 1982
The Roman Empire by Colin Wells, Standford University Press, Stanford, 1984