Originally corps were to consist of approximately 100 all ranks under the command of a captain, with some localities having subdivisions of thirty men under a lieutenant. The purpose of the rifle corps was to harass the invading enemy’s flanks, while artillery corps were to man coastal guns and forts. Although not mentioned in the circular letter, engineer corps were also formed, principally to place underwater mines for port defence. Stretcher-bearers attached to the rifle corps subsequently formed volunteer medical detachments affiliated to the Army Medical Corps. In a handful of counties, units of light horse or mounted rifles were formed.