A field force in British, Indian Army and Tanzanian military parlance is a combined arms land force operating under actual or assumed combat circumstances,[1] usually for the length of a specific military campaign.
Examples are: In Australia, a field force comprises the units required to meet operational commitments.
In the United States, during the Vietnam War the term came to stand for a corps-sized organization with other functions and responsibilities.
Unlike an Army corps, which had a size and structure fixed by Army doctrine, the field force could expand as needed and had other functions such as liaison with South Vietnamese and civil affairs functions and was flexible enough to have many subordinate units assigned to it.
[3] In counterinsurgency type campaigns, select and specially trained units of police armed and equipped as light infantry have been designated as police field forces who perform paramilitary type patrols and ambushes whilst retaining their police powers in areas that were highly dangerous.