Decimation was the way Rome punished army units for crimes like cowardice. One soldier out of ten would be randomly killed.
The only random thing about it was where people stood in line. Otherwise, they counted off 1 to 10. I suppose there could be additional randomness when the Master Sergeant said, "All number such and such step forward," randomness in the form of a riot.
I believe the boys who fought Sparticus's army experienced decimation as sort of a motivator. It worked.
The Romans also used this socializing technique with newly assimilated towns if the local town folk didn't want to be assimilated. That also worked for a bit. In the end they faced folks as tough as they were who were more benign in the taxation department. Then the boys on imploding concentric circles decided that Pax Romana wasn't worth the cost.
Like most tyrannies, the Roman Empire was as bad as any and worst than most, starting at least as far back as the days of Julius Caesar. Decimation was but one manifestation.
These days when some newsie or other clown wants to sound erudite by using the word "decimate" or some permutation, it makes me want to puke. Such bozos need to read a bit...if they can read.