A penal military unit, also known as a penal formation, disciplinary unit, or just penal unit (usually named for their formation and size, such as penal battalion for battalions, penal regiment for regiments, penal company for companies, etc.), is a military formation consisting of convicts mobilized for military service. Such formations may consist of military prisoners convicted under military law, civilian prisoners convicted in civilian courts, prisoners of war who have chosen to side with their captors, or a combination of these groups.
Service in penal military units is generally considered a form of punishment, discipline, or penal labour, used in lieu of, or offered as an alternative to, imprisonment or capital punishment. Penal units have historically been used as disposable cannon fodder, treated poorly or with little regard and used in compromising or dangerous situations (commonly suicide missions such as demining or forlorn hope advance parties), as march battalions that maintain replacement personnel as reserves, or kept in the rear for military operations other than war or menial labour relating to the war effort, guarded and overseen by regular military units, military police, or barrier troops to ensure they do not attempt to escape, retreat, or mutiny. However, this is not always the case: some penal units are treated the same as regular units and, depending on military organization, a dedicated penal unit may not exist at all, with convicts instead being placed in a regular unit. Rewards and incentives for convicts to serve in a penal unit vary—often expungement, commutation, stay of execution, or a pardon—though penal units used as punishment typically lack those by nature.
