Decimation (from the word decimatio) was one of the most famous and harsh punishments used against a cowardly or rebellious group of soldiers in the Roman army.
The unit sentenced to be decimated (e.g. a cohort) was divided into groups of ten soldiers. Everyone drew lots (so-called sortition) and the one who failed (had the shortest straw) was killed by his nine companions by stoning or beating with sticks (so-called fustuarium). Survivors received barley instead of wheat and were punished with additional quarters outside the fortified camp until they wiped their offences in battle.
What is important, however, was that this punishment was not only carried out on rank-and-file legionaries – it also included centurions and warrant officers. In practice, decimation has not been abused throughout history due to a serious weakening of personal status.
Decimation was also used by Marcus Licinius Crassus in 71 BCE. during the Spartacus uprising. As a result, about 50 people died after the decimation of the whole cohort. Julius Caesar used the threat of decimation of his 9th legion – during the war with Pompey – to calm down the rebellious mood.
Description of the decimation has left us Plutarch. During the war with the Parthians in 36 BCE, Antonius used it.
Antony was furious and employed the punishment known as “decimation” on those who had lost their nerve. What he did was divide the whole lot of them into groups of ten, and then he killed one from each group, who was chosen by lot; the rest, on his orders were given barley rations instead of wheat
– Plutarch from Cheronea, Antony, 39
In 39 BCE Domitius Calvinus – as the proconsul in Spain – conducted warfare against the Iberian tribes. In one of the battles, a high-ranking officer was killed, which turned out to be due to the cowardice of the centurions subordinate to him. Calvinus decided to decimate two centuries, resulting in the most important centurion in the primus pilus Vibilius.
The decision was also used during the empire. He used it, among others Octavian Augustus in 17 BCE or Galba when coming to power. Emperor Macrinus (reigned in 217-218 CE) introduced a “lighter” form of decimation – centesimatio, that is, killing every hundredth soldier.