An auxiliary force is an organized group supplementing but not directly incorporated in a regular military or police entity. It may comprise either civilian volunteers undertaking support functions or additional personnel directly performing military or police duties, usually on a part-time basis.
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 armies 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). Specialist units of slingers, scouts, archers and camel mounted detachments continued in existence as separate units with a regional recruitment basis.
United Kingdom and British Empire
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.
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. Their average life span was two weeks, and 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.
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:
- Royal Maritime Auxiliary Service a former auxiliary to the Royal Navy
- Royal Naval Auxiliary Service a former auxiliary to the Royal Navy
- Royal Naval Minewatching Service a former auxiliary to the Royal Navy
- Royal Naval Supply and Transport Service a former auxiliary to the Royal Navy
- Royal Observer Corps a former auxiliary to the Royal Air Force
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.
Current military or governmental auxiliaries
- Flygvapenfrivilligas Riksförbund (Air Force Volunteers Association) as an auxiliary of the Swedish Air Force
- Frivilliga Flygkåren (FFK) an auxiliary of the Home Guard (Sweden)
- Frivilliga radioorganisationen (Radio Voluntary Organisation) as an auxiliary of the Home Guard (Sweden)
- Riksförbundet Sveriges lottakårer (National Association of Sweden Lotta Corps) an auxiliary of the Home Guard (Sweden)
- Svenska Fallskärmsförbundet (Swedish Parachute Association) as an auxiliary of the Home Guard (Sweden)
- Sjövärnskåren (Swedish Naval Volunteers) an auxiliary of the Swedish Navy and Home Guard (Sweden)
- Royal Fleet Auxiliary of the British Royal Navy
- Special Constabulary, auxiliary police to various Police Services in the UK.
United States of America
- Civil Air Patrol as an auxiliary of the United States Air Force
- Military Auxiliary Radio System as a civilian auxiliary of the United States Armed Services
- United States Coast Guard Auxiliary as an auxiliary of the United States Coast Guard
- United States Naval Sea Cadet Corps as an auxiliary of the United States Navy and to some extent the United States Coast Guard
- United States Merchant Marine as an auxiliary of the United States Navy
- Concise Oxford Dictionary, ISBN 0-19-861131-5
- Pakenham, Thomas. The Boer War. pp. 542 & 571. ISBN 0-7474-0976-5.