David M. Carr in Salon:
It is important to get clear on what ancient crucifixion was. The word “crucifixion” comes from the Latin word cruciare— “torture.” The Roman Cicero describes it as suma supplicum, “the most extreme form of punishment,” and goes on to say: “To bind a Roman citizen is a crime, to flog him an abomination, to slay him is almost an act of murder, to crucify him is—what? There is not a fitting word that can possibly describe so horrible a deed.” The Jewish historian Josephus describes it as “the most pitiable of deaths.” The victim was first brutally whipped or otherwise tortured. Then his arms were attached to a crosspiece of wood, usually by nails, sometimes by rope. Finally, the victim was hoisted by way of the crosspiece (crux in Latin) onto a pole, and the crosspiece was attached to the pole so that his feet did not touch the ground. There the victim was left on public display until he died. Sometimes death came quickly through suffocation or thirst, but sometimes death was postponed by giving the victim drink. After the victim was dead, the Romans often left the body on the cross as a public display, rotting and eaten by birds. The point was not just to hurt and kill a person but to utterly humiliate a rebel or upstart slave, while terrorizing anyone who looked up to them. Crucifixion was empire-imposed trauma intended to shatter anyone and any movement that opposed Rome.
More here.