Decimation (punishment)

The historicity of the punishment during the early and middle republic is questioned, and it may be an ahistorical rhetorical construct of the late republic. Regardless, the first well-attested instance was in 72 BC during the war against Spartacus under the command of Marcus Licinius Crassus. Further instances followed in the next century, mostly occurring during times of civil strife, before falling out of use after AD 69. There is evidence of the punishment's revival in the post-classical world, such as during the Thirty Years' War and World War I.

In modern English, the word is used most commonly to mean total destruction or annihilation.

In ancient Rome

Decimation was the most extreme punishment of the Roman army, where a tenth of a unit that had proven its cravenness was killed. The Romans believed that it had ancient roots in the early republic – the fifth and fourth centuries – and the theoretically unlimited powers of the Roman magistrate militae ("on campaign"). The procedure for decimation, as described by Polybius, involved a soldiers' assembly before the tribunes. Then, of the units adjudged cowardly, lots were taken such that a tenth of the men were condemned. Their comrades then killed them with clubs before the survivors were then further punished with barley rations and required to bivouac outside the fortified camp.

The practice was rare: there are only eleven recorded instances. Five of them date to the late republic from its revival in 72 BC with a further four during the triumviral and civil wars prior to Actium.

Questionable historicity

There is a single instance recorded by Livy that predates the middle republic, that of Appius Claudius Crassus Inregillensis Sabinus in 471 BC, but anachronistic elements of the narrative there suggest ahistoricity. The middle republican writer Polybius, however, in a detailed narrative, suggests that by the middle republic it was established, if not in practice at least otherwise, as a rhetorical construct. Two other instances are reported in Frontinus but are undated. Associated with the careers of Fabius Rullianus and an unknown Aquilius, these events (if historical) could not have taken place after 259 BC.

Literary evidence relating to punishment for military offences in the middle republic generally indulges in rhetorical exaggerations. If any instances of decimatio occurred between c. 315 BC and the historical instance under Crassus in 72, they were likely small enough not to be recorded. Indeed, the Polybian narrative suggests counts of victims fewer than twenty. If expanded by a factor of ten, the units involved were small and did not exceed c. 200 men. The presence of other non-lethal punishments meted for cowardice and lapses of military discipline – eg demotion, exile of Sicily, subsistence on barley rations, pay deductions, etc – that are well documented in the sources of the period also suggest that decimatio was essentially a rhetorical myth.

By the early second century BC, the extension of provocatio rights to the military also made it illegal for magistrates to kill or scourge their citizen soldiers, with similar rights also extended late in the second century to allied soldiers under Roman command. Cases of soldiers collectively resisting mass punishments and the necessity of their active participation also suggest that decimation was not at all commonly practicable. Moreover, actual practice of decimation would have alienated Roman citizen voters from the presiding general, who was accountable before both the law courts and the voters.

Revival during the first century

The first historical instance of decimation was in 72 BC under the command of Marcus Licinius Crassus during the Third Servile War. A unit of 500 men who fled from battle was decimated, with some fifty men executed. The narratives in Appian that Crassus decimated either two legions or his entire army (producing fatalities of around 1,000 and 4,000 respectively) are rejected as exaggerations.

The historian Michael Taylor identifies three major factors for this revival. First, the war being fought was against a slave revolt and therefore constituted a genuine emergency for the Roman state, especially after the defeat of that year's consuls' armies. Second, the ascendency of the Sullan regime in the aftermath of the recent civil war and its proscriptions may have set a precedent for ignoring citizen provocatio rights against arbitrary punishment. Third, there was at the time an elite antiquarian intellectual movement which may have suggested to Crassus the hitherto unprecedented option to reviving a punishment last used, if at all, centuries previously. Indeed, by the first century BC, the Romans had no knowledge of the practice's origins. The exigencies of the moment may have been sufficient to insulate Crassus from any social or political punishment for his unprecedented actions, which may have also set the precedent for ignoring provocatio rights on campaign, even if contrary to law.

After Crassus' use in 72 BC, the next possible instances were under Julius Caesar in 49 BC and Mark Antony in 44. However, both were applied only to small groups (in the former killing a tenth of the 120 ringleaders of a mutiny) or with a smaller proportion (in the latter Cicero describes only a targeted killing of supposedly disloyal centurions). Further instances appear during the civil war where Caesar's soldiers demand decimation to forego demobilisation in the aftermath of mutiny or defeat. In these instances, decimation was brought up essentially to demonstrate absolute loyalty to Caesar, who in all cases refused. The latter instance, if Appian is to be believed, also failed to restore discipline, instead increasing anger against Antony's command. A further instance in 39 BC under Gnaeus Domitius Calvinus, proconsular governor of Spain, is documented in Dio: however, the more contemporary source Velleius Paterculus reports only the execution of the fleeing unit's commander.

The next firmly documented instance was in 36 BC when Mark Antony decimated two cohorts after defeats against the Parthians, producing some 80 fatalities. Plutarch's biography attests that after a defeat in Media:

Antony was enraged, and visited those who had played the coward with what is called decimation. That is, he divided the whole number of them into tens, and put to death that one from each ten upon whom the lot fell. For the rest he ordered rations of barley instead of wheat.

A second instance follows in 34 BC under Octavian for a unit which fled during his campaign in Illyricum. After this instance in 34, over fifty years elapse before the next under Lucius Apronius c. AD 18–20 for defeats in Numidia and then another fifty years elapse to Galba's usage during the Year of the Four Emperors against a unit of soldiers who refused to be demoted to naval service.

Late antiquity

G. R. Watson notes that "its appeal was to those obsessed with nimio amore antiqui moris" – that is, an excessive love for ancient customs – and notes, "decimation itself, however, was ultimately doomed, for though the army might be prepared to assist in the execution of innocent slaves, professional soldiers could hardly be expected to cooperate in the indiscriminate execution of their own comrades". After the Principate, the punishment also falls into obscurity until late antiquity, when it may have been used by the emperor Julian during his Persian campaign. The emperor Macrinus instituted a less harsh centesimatio, the execution of every 100th man.

The Eastern Roman Emperor Maurice forbade in his Strategikon the decimatio and other brutal punishments. According to him, punishments where the rank and file saw their comrades dying by the hands of their own brothers-in-arms could lead to a collapse of morale. Moreover, it could seriously deplete the manpower of the fighting unit.