Auxiliary may be military volunteers undertaking support functions or performing certain duties such as garrison troops, usually on a part-time basis.
Some auxiliaries, however, are militias composed of former active duty military personnel and actually have better training and combat experience than their regular counterparts.
The term originated with the Latin eponymous Auxilia relating to non-citizen infantry and cavalry serving as regular units of the Roman Empire.
As the Roman army of the Republican and early Empire periods was essentially based on the heavy infantry who made up the legions, it favored the recruitment of auxiliaries that excelled in supplementary roles.
These included specialists such as missile troops (e.g. Balearic slingers and Cretan archers), cavalry (recruited among peoples such as the Numidians, and the Thracians), or light infantry.
The Horse and Foot Guards were considered parts of the British Army, though falling under the Royal Household there were differences in their command and administration.
Although still meant to be local service, this force sent drafts of volunteers to regular battalions, and then entire units, overseas during the First World War.
Recruited in significant numbers towards the end of the war from Afrikaner prisoners and defectors, they were known as hensoppers ("hands-uppers" i.e. collaborators) by their fellow Boers.
Recruited from former officers of the British Army who had served during World War I, the Auxiliary Division was a motorized mobile force nominally forming part of the Royal Irish Constabulary.
In 1941, the British government created an organization of Auxiliary Units in southern England, capable of waging a guerilla war against occupying forces should Britain be invaded by the Nazis.
[26] During the Algerian War of 1954–62 large numbers of Muslim auxiliaries (Harkis) were employed in support of regular French forces.
The term had also been applied to some units created in 1933 by the early Nazi government (mostly from members of SA and SS) and disbanded the same year due to international protests.
[30][31][32] Certain German auxiliary units, such as the Reserve Police Battalion 101, committed horrendous massacres of Jewish, Romani, and other targeted ethnic groups while serving with the Wehrmacht and Einstazgruppen in Eastern Europe.
Throughout their service on the Eastern Front, when ordered to execute civilians en masse, members of the Battalion were frequently given the opportunity to reject participation in the events in lieu of standing guard at the perimeter or other less violent tasks.
[33] While a minority was generally able to escape participation in the acts, most were willing volunteers, succumbing to social pressures pushed by an atmosphere of shared guilt and fervent hypermasculine nationalism.
[35] Correspondingly, girls as young as 14 years old were trained in the use of small arms, panzerfausts, machine guns, and hand grenades throughout the war.
[36] Hiwis were auxiliary forces recruited from the indigenous populations in the areas of Eastern Europe first annexed by the Soviet Union and then occupied by Nazi Germany.