Auxiliaries are personnel that assist the military or police but are organised differently from such forces. Auxiliary may be volunteers undertaking support functions or performing certain duties such as garrison troops, usually on a part-time basis. Unlike a military reserve force, an auxiliary force does not have the same degree of training as regular soldiers or integration into a fighting force. Some are former military active duty personnel and actually have more training than their counterparts.
Historically the designation auxiliary has also been given to foreign or allied troops in the service of a nation at war. In the context of colonial troops, locally recruited irregulars were often described as auxiliaries.
Auxiliaries in the Roman army were recruited from provincial tribal groups who did not have Roman citizenship. 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. Auxiliaries were not paid at the same rate as legionaries, but could earn Roman citizenship after a fixed term of service.
By the 2nd Century AD the auxiliaries had been organised into permanent units, broadly grouped as Ala (cavalry), Cohors (infantry) and Cohors equitata (infantry with a cavalry element). Both cavalry alae and infantry cohors numbered between 480 and 600 men each. The mixed cohors equitata usually consisted of 6 centuries of foot soldiers and six squadrons of horsemen. Specialist units of slingers, scouts, archers and camel mounted detachments continued in existence as separate units with a regional recruitment basis.
During the Second Boer War Boer auxiliaries were employed by the British Army under the designation of "National Scouts". 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.
Prior to the creation of the Territorial Force in 1908, the term "Auxiliary Forces" was used by the British Army to collectively cover Yeomanry, Militia and Volunteers. That is to say the various part-time units maintained to act in support of the Regular Army (UK).
The Auxiliary Division was a British paramilitary police unit raised during the Irish War of Independence 1919-21. 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 who would wage a guerilla war against occupying forces should Britain be invaded by the Nazis. Since the invasion never came, they were ultimately never used in combat. The Auxiliary Units were meant to carry out assaults on German units, along with damaging train lines and aircraft if necessary.
Whilst working as full-time, active duty personnel, the women's services of WWII were titled as or seen as auxiliaries to the male services. These services were:
The Royal Auxiliary Air Force was originally an auxiliary of the Royal Air Force, when it was first conceived and formed in 1924. Today the RAuxAF acts as a military reserve; this is reflected in its more common name 'RAF Reserve'.
Other former British military or governmental auxiliary organizations included:
Auxiliary organizations of other countries of the British Empire:
France made extensive use of tribal allies (goumiers) as auxiliaries in its North African possessions. During the Algerian War of 1954-62 large numbers of Muslim auxiliaries (Harkis) were employed in support of regular French forces.
German paramilitary police forces, called Hilfspolizei or Schutzmannschaft, were raised during World War II and were the collaborationist auxiliary police battalions of locally recruited police, which were created to fight the resistance during World War II mostly in occupied Eastern European countries. Hilfspolizei refers also to German auxiliary police units. There was also a HIPO Corps in occupied Denmark. 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.
With an increase in the amount of men needed to serve on the front lines, women were allowed to serve as auxiliaries to the Wehrmacht, known as Wehrmachthelferin, to take over duties within Germany freeing up men. From 12 February 1945, the Nazis conscripted German women and girls into the auxiliaries of the Volkssturm. Correspondingly, girls as young as 14 years were trained in the use of small arms, panzerfausts, machine guns, and hand grenades from December 1944 through May 1945.
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. Adolf Hitler reluctantly agreed to allow recruitment of Soviet citizens in the Rear Areas during Operation Barbarossa. In a short period of time, many of them were moved to combat units.