Duncan Alexander Cameron is said to have been born on 19 December 1808, the son of Sir John and Lady Cameron. His mother's birth name was Brock. Duncan Cameron's forebears, descended from the chiefs of their clan, after 1745 pursued careers in the British army. Sir John Cameron acquired a reputation as a fighting colonel in the Peninsular campaign, and reached the rank of lieutenant general. He attended Eton College; his son may have also. Lady Cameron was related to Admiral Lord Saumarez, a Guernseyman, and the family may have spent some years on Guernsey, where Sir John died in 1844.
Duncan Cameron was commissioned ensign in the 42nd Regiment (the Black Watch) on 8 April 1825. Thanks to his connections and ability, promotion was relatively swift: he was made lieutenant on 15 August 1826, captain on 21 June 1833, and major on 23 August 1839. He became lieutenant colonel on 5 September 1843, while commanding a battalion of his regiment on Malta. Cameron made his name during the 1850s. In the Crimean War he briefly led his battalion before being made commander of the Highland Brigade, in succession to General Colin Campbell, Lord Clyde, who became his patron. Cameron led the brigade with distinction at the battles of Alma and Balaclava and at the siege of Sebastopol. In the assault on the Redan on 18 June 1855 he found Frants Todleben's military engineering almost as much of a problem as he was later to find Rewi Maniapoto's. Cameron received honours for his Crimean services, including promotion to (local) major general on 9 November 1855, a CB, and Turkish, French, and Sardinian decorations.
As well as achieving fame in battle, Cameron became well known for his contribution to the education of army officers. In 1857 he was appointed vice president and de facto head of the Council for Army Education; the Duke of Cambridge, commander in chief, was nominal president. Cameron made some progress in reforming the Royal Military College and Staff College at Sandhurst. On 25 March 1859 he was promoted permanent major general. In 1860 he received command of the troops in Scotland, an appointment prized among Scots officers. His next posting, in 1861, was even more highly valued: chief command of an army at war, in New Zealand. At this watershed in his career Cameron was considered one of the most accomplished officers in the British Army. His reputation could hardly have been equalled among junior generals. Five years in New Zealand were to change all that.
Dissatisfied with the progress of the Taranaki war, the War Office promoted Cameron to (local) lieutenant general on 23 January 1861, and sent him to New Zealand to replace Major General T. S. Pratt. Cameron arrived at New Plymouth in late March and as his first duty had to tell Pratt of his supersession. Pratt's staff were astonished and indignant, but the local settlers initially found Cameron's presence 'wonderfully reviving'. Cameron was keen 'to have a brush' with the Māori, but ironically he arrived at the conclusion of the Taranaki war. However, Governor Thomas Gore Browne was planning an invasion of Waikato to crush the Māori King movement and, at a meeting of the New Zealand Executive Council, Cameron enthusiastically supported this course. 'I strongly recommended that they [the Kingites] should be called to account, without loss of time, for their participation in the [Taranaki] rebellion'. Then, in mid 1861, Browne was sacked and replaced by Governor George Grey, and, to Cameron's bitter disappointment, the invasion was called off. Balked of the war he had come out to fight, Cameron apparently sent in his resignation in early 1862, but the War Office declined to accept it. Grey consoled Cameron by hinting that the invasion had merely been postponed, and by authorising active preparations for it. But, as Grey seemed to vacillate, his relationship with Cameron wavered between efficient co-operation and mutual recrimination, as it was always to do.
On 4 June 1863 Cameron made a well-organised and successful attack on Katikara in Taranaki, in revenge for an ambush of British troops the previous month. The size of the defeated Māori force was wildly exaggerated; this was clearly a side-show. Cameron returned to Auckland to await Grey's decision on Waikato. Finally, on 12 July 1863, the long-delayed invasion began, and Cameron embarked on his life's great work: the attempt to destroy Māori independence. Cameron planned to advance steadily on the Waikato heartland, using his great superiority in numbers and supplies, and to force the Māori into a decisive battle which would end the war quickly. The Māori, under Rewi Maniapoto and Tāwhana Tīkaokao, opposed him with a defensive line centred on Meremere. They also used the strategy of raids on the British lines of communication. Although the British had a minor victory at Koheroa on 17 July, the Māori raids prevented Cameron from concentrating enough troops to attack Meremere until 30 October. When he finally did attack, the Māori escaped without loss. Cameron was blamed for the wholly unexpected delay of three months before the advance on Meremere, and it is true that the Māori had won the first round.
Nevertheless Cameron moved on up the Waikato River. The Māori army had had to disperse for economic reasons; he attacked the rump of it at Rangiriri on 20 November. Eight British assaults were repulsed, but one was partially successful and Cameron managed to take the pā and 180 prisoners by unscrupulously manipulating a flag of truce. Ironically, for this victory he received the KCB on 20 February 1864. Cameron continued his advance until confronted by the Pāterangi line, the most formidable group of pā the Māori had ever built, protecting the Kingites' richest agricultural area and garrisoned by their strongest army. On 20–21 February 1864, in easily his greatest military achievement, Cameron brilliantly outflanked this line and took it and the whole district at low cost, gravely and permanently weakening the King movement. Many Māori still believe that he managed this by breaking an agreement on the neutrality of the village of Rangiaowhia, where Kingite non-combatants were assembled. However, it seems that this notion of an agreement was founded on a misunderstanding. Cameron escaped criticism for Rangiriri, when he deserved it, and received it for Rangiaowhia, when he did not.
Cameron had still to achieve the clear-cut combat victory he so desired. The partly successful siege of Ōrākau from 31 March to 2 April did not count, and when an opportunity presented itself at Tauranga, Cameron halted operations in the Waikato basin and took his striking force east. The coastal location of the Māori position, the Gate pā, enabled him to concentrate crack troops and a vast artillery train against it. His preparations for battle on 29 April were impeccable, but his assault force was routed. Despite his reputation for stoicism, 'the general dashed his field-glass on the ground, turned his back on the fugitives, and retired to his tent to conceal his emotion.' This disaster was partly redeemed at Te Ranga on 21 June, when British forces stormed an incomplete pā, but Cameron rightly concluded that frontal assaults against complete trench-and-bunker earthworks were fruitless. This meant that the much desired 'decisive blow' was impossible. 'And if Her Majesty's troops are to be detained in the colony until one is struck', he wrote, 'I confess I see no prospect of their leaving New Zealand.'
Cameron undertook one more campaign: an invasion of South Taranaki in the first half of 1865. It was here that he allegedly earned the Māori sobriquet 'The Lame Seagull' for slowness and timidity. In fact his operations were efficient and effective, if cautious. He won substantial victories at Nukumaru on 24–25 January and at Te Ngaio on 13 March, but wisely refused to attack the modern pā of Weraroa. It was primarily this refusal which led to the utter collapse of co-operation between him and Grey from mid April. Grey, who always outclassed Cameron in the art of self-promotion, 'took' Weraroa himself in July, long after it had lost its strategic significance, and after the small remaining garrison had indicated a willingness to surrender. Cameron's poor historiographical reputation stems largely from this little farce. Well before the incident, on 7 February 1865, Cameron had sent in his resignation. This time it was accepted, and he left the country on 1 August.
Cameron's remaining career contained some satisfactions. He was promoted permanent lieutenant general on 3 June 1868, full general on 5 December 1874, and received the GCB on 24 May 1873. He was comfortably off, as he had been colonel of his regiment since 1863 and had been bequeathed £3,000 by Lord Clyde the same year. He served on a royal commission into military education, his old speciality, in 1867, and was governor of the Royal Military College, Sandhurst, from 1868 to 1875, when he retired. He married Louisa Flora Maclean, his deputy's daughter, at Kew, Surrey, on 10 September 1873 but she died on 23 September 1875. There were no children. Through letters and publications from New Zealand he was painfully reminded of the damage that had been done to his military reputation there. A bizarre vendetta helped to keep old wounds open. The unbalanced Captain A. H. H. Mercer, whose brother had died at Rangiriri, accused Cameron of cowardice at that battle, challenged him to duels, and published half a dozen strange booklets maligning him. Beset by illness in his last years, Cameron died at Cambridge House, Kidbrook, Kent, on 8 June 1888.
Cameron was 'a tall man, with a large hookey nose and small grey eyes.' His personality is difficult to recover, but in spite of a stereotypically curt and cold manner he seems to have had a capacity to inspire loyalty and affection among those close to him. One officer even wrote of 'our beloved General', although this was probably a minority view. He had real moral and physical courage: he stood up to Grey, disregarded settler opprobrium, and advanced, unarmed, 20 yards in front of some hesitant troops at Koheroa. He was recommended for the Victoria Cross for this last incident, a request denied on the grounds that a commanding general had no business risking his own life.
The traditional New Zealand assessment of Cameron is that he was high-minded but slow and uninspired. Both conclusions are questionable. In 1865 he did disparage colonial land-grabbing and bemoaned having to fight a war for it, but these moral doubts came very late and coincided neatly with his frustration at finding decisive victory impossible. He eagerly advocated the invasion of Waikato, and his conduct at Rangiriri might have cost him his commission if his foes had been white. Denigration of Cameron's competence is as unsound as praise of his scruples. A good tactician, a very good strategist, and a superb organiser, he was the best European commander to serve in New Zealand, and among the best of Victorian generals: a Garnet Wolseley without the charisma. With Grey, he tipped the balance of power between Māori and Pākehā in favour of the latter. He was deprived of due credit, first by Māori fighters, who, with their revolutionary modern pā, prevented him from achieving outright victory, and next by Pākehā writers, who attributed his lack of success in battle to incompetence. Yet his influence was profound: it was Duncan Cameron at Pāterangi, not William Hobson at Waitangi, who sounded the death-knell of Māori independence.