On 16 May 1849, as a family man without notable career prospects, Haultain emigrated to Auckland, New Zealand, on the Oriental Queen, in charge of the 8th Detachment of the Royal New Zealand Fencible Corps, military pensioners who were settled in villages to protect the southern approaches to Auckland.

Haultain took a number of public positions, becoming a member of Auckland's first borough council on 18 November 1851 and resident magistrate at Onehunga in 1855 and at Howick in 1856.

Haultain's life had settled into the easy domesticity of the retired soldier but the outbreak of fighting in Taranaki in 1860 changed all that.

Haultain was asked by the Stafford government to help organise a defence force and he became on 26 April 1860 lieutenant colonel of the 1st Battalion, Auckland Militia.

In March 1864, while garrisoning the redoubt at Kihikihi, Haultain was informed that Maori entrenching parties were building fortifications at Orakau.

His instructions from the defence minister were to settle the troops around strategic villages guarding the confiscation line.

In February 1865, the new Weld government instructed Haultain to remove all the remaining soldiers from the pay and ration lists.

He resigned his commission in mid-1865 to free himself for politics, and in particular to express his opposition to Weld's policy of seeking the withdrawal of the imperial regiments.

Stafford was happy to agree, but pressures of economy and of holding together the fractious provinces in time turned the policy of self-reliance inside out.

By early 1867, he had come to accept that if the imperial troops 'are not to be at our disposal, we had better be without them – but then I don't see how the defence of the Northern Island is to be maintained by the small quota of Police we proposed to raise.'

This battered army was the colony's only strike force, and by November 1867, Te Kooti on the East Coast had become an equally alarming threat.

He ordered the remaining forces on the west coast withdrawn to a defensive line on the outskirts of Wanganui, and Whitmore and the Armed Constabulary were shipped to Napier.

The colonists had successfully defended themselves and in the process Haultain's Armed Constabulary had become effective light infantry.

He avoided interference with his commanders, backed up Whitmore and concentrated on providing the practical support that would enable him to succeed.

Ironically, since he had taken office with strong misgivings about the self-reliant policy, he as much as anyone can be credited with making Weld's dream work in practice.

[5] Botanist Elizabeth Stack noted in her journal in 1859 that Captain Hainault offered to help her identify her moss and fern specimens.