Penal military units, Penal battalions, penal companies, etc., are military formations consisting of convicted persons mobilized for military service. Service in such units is considered a form punishment or discipline as opposed to imprisonment or capital punishment.
Dedicated penal units were first envisioned during the Napoleonic era of warfare, as large armies formed of conscripts often suffered from disciplinary problems. Soldiers who refused to face the enemy were seen as detrimental to the cohesion of the army and as a disgrace to the nation. The formation of penal battalions was seen as a way of disciplining an army and keeping soldiers in line. In addition, many nations conscripted criminals into penal battalions in lieu of imprisoning them during wartime to better utilize national manpower. Such military units were treated with little regard by the regular army and were often placed in compromising situations, such as being used in forlorn hope assaults.The French Empire in particular was notable for employing penal military units during the wars of the coalition, especially during the later years of the conflicts as manpower became limited. The Régiment pénal de l'Île de Ré, formed in 1811 and composed almost entirely of criminals and other societal undesirables, would see action during the later years of the Napoleonic Wars.
The disbandment of conscripted armies and end of large scale warfare following the Napoleonic era lead to the decline of the penal battalion system in continental Europe. However, the system continued in overseas colonies, again with the French as the primary employers of penal battalions. The Battalions of Light Infantry of Africa (Bats d'Af) was formed by order of Louis Philippe I in 1832 for the purpose of expanding the French colonial empire. The Battalion fought in the French conquest of Algeria and during the Crimean War. The French also employed the Compagnies d'exclus ("companies of the excluded"), military units which were stationed at Aîn-Sefra in Southern Algeria. These penal units consisted of convicts condemned to five years or more of hard labor and were judged unworthy to carry weapons.