After the signing of the Treaty of Waitangi, British troops were stationed in New Zealand in varying numbers from 1840 to 1870 and, until the middle sixties, provided the chief protection for the colonists and bore the brunt of the fighting against the Maoris. The first troops to land in New Zealand were a detachment of the 80th Regiment which arrived from Sydney in April 1840, and 30 years later the last of the Imperial troops to depart were the main body of the 18th (Royal Irish Regiment), in February 1870. Throughout this period of New Zealand's history, British forces other than regiments of the line, served here. These consisted of naval detachments, Royal Marines, Royal Engineers, Royal Artillery, and the Commissariat and the Waggoners (the predecessors of the Royal Army Service Corps).

From a strength of a few hundred men in the early 1840s, the Imperial Government decided in 1847 to maintain, for the time being, 2,000 regular troops in the colony. Over the next 12 or 13 years this number varied, and in 1860 about the time of the outbreak of the first of the later Maori Wars, the strength of the British forces was down to approximately a thousand men. These troops, consisting of the 65th Regiment and detachments of artillery and engineers, were scattered in five different stations, at Auckland, Wellington, Napier, Wanganui, and New Plymouth. By the end of 1865, the Imperial forces in the colony totalled about 10,000 men, consisting of the 12th, 14th, 18th, 40th, 43rd, 50th, 57th, 65th, 68th, and 70th Regiments, two batteries of Field Artillery, and Royal Engineers and Military Train.

The presence of these troops in New Zealand became a problem for the British and New Zealand Governments. On the one hand, the Imperial Government was extremely critical of various aspects of the New Zealand Government's attitude towards the Maoris, especially over the matter of confiscation of land. On the other hand, differences of opinion developed over the tardy conduct of operations, for the colonists – in theory – were paying £40 per annum for an infantryman and £70 per annum for a gunner. These circumstances led to the adoption by the New Zealand Government, late in 1864, of its “self reliant” policy, the substance of which was to dispense with the services of Imperial troops and to trust to local forces and Maori auxiliaries to carry on the war. For its part, the Imperial Government welcomed the proposal, for it considered the colony with its growing population should be able to fend for itself. From 1866 onwards the gradual withdrawal of Imperial troops commenced, and after Chute's vigorous campaign in Taranaki, early in 1866, with mixed forces. Imperial and colonial, operations against hostile Maoris were conducted by colonial forces.

During this year the following regiments departed from New Zealand – the 70th, 43rd, 68th, 40th, 14th, and half of the 50th. Four more departed in 1867, leaving only the 18th. Early in 1869 this regiment was under orders to depart, but because of alarm felt by colonists about the guerilla war waged by the elusive Te Kooti in the Poverty Bay and Bay of Plenty areas, General Chute, on his own responsibility, detained the 18th, which did not finally depart until February 1870.

The following list of regiments that served in or sent detachments to New Zealand is divided into two sections. In the first group are those regiments which have lost their identity since the 1957 amalgamation plan, and in the second group are those which retained their identity.