Robert Logan was born at Langton, Berwickshire, Scotland, on 2 April 1863, the son of Euphemia Helen Logan and her husband, Thomas Logan, a tenant farmer. He was educated at Edinburgh Academy. Arriving in New Zealand in 1881, he worked as a station hand in Southland before purchasing his own sheep run, Maritanga, two years later in Otago's Maniototo district. He married Elizabeth Catherine Preston at Fortrose, Southland, on 16 April 1890; they had four sons, one of whom died in infancy. Elizabeth died in 1910 and about 1914 Logan married Eleanor Mary Preston, with whom he had two daughters.
Logan was active in local government, becoming a member of the Maniototo County Council in 1888 and chairman from 1901 to 1902. He raised the Maniototo Mounted Rifle Volunteers in 1900 and joined the 1st Otago Mounted Rifle Volunteers in 1904. He was promoted to major and then to lieutenant colonel in 1908. In March 1911 Logan was made an honorary aide de camp to the governor general and in June 1912 he became a temporary colonel in the regular army. He was appointed officer commanding the Auckland Military District, moved to Auckland and sold his sheep run. He was to become a full colonel in October 1915.
At the outbreak of the First World War Logan was appointed to command the 1,383-strong expeditionary force to capture German Samoa (afterwards renamed Western Samoa) as 'a great and urgent Imperial Service'. The Germans were in no position to offer resistance and on 29 August 1914 Logan assumed responsibility as military administrator. He held this position throughout the war, by 1918 governing some 38,000 Samoans and another 1,500 Europeans, of whom over one-third were Germans.
Logan was given wide latitude in his new role; he was bound only by the rules of war and, more specifically, the 1907 Hague agreement on occupied territories. After 14 years of German rule Samoa had a thriving plantation economy and political stability, and it made sense to govern his inheritance much as he found it. Although most German officials were dismissed and replaced by New Zealanders, Samoa was administered along existing lines in so far as the exigencies of war allowed. German trade and plantations were permitted to continue largely unimpeded with the proviso that external trade in plantation produce be conducted with Allied or neutral countries. In 1916, however, when it became evident that German firms were still trading with Germany, they were liquidated and placed under New Zealand receivership. The repercussions of this move were considerable: by far the largest of these firms, Deutsche Handels- und Plantagen-Gesellschaft der Südsee-Inseln, financed many smaller planters, who mostly went bankrupt; a cloud of uncertainty descended over Samoa's economic future.
Another cause of economic uncertainty and planter disaffection was more of Logan's making. Most of the plantations depended on indentured Chinese labourers. There were 2,184 in Samoa in 1914 and soon after Logan's arrival they mounted a protest against being short-rationed. The uprising was promptly suppressed and so alarmed was Logan about this 'menace to the European population' that German planters were permitted to carry firearms for protection. Such was his hostility towards Chinese that in 1915 he refused to extend the Chinese labourers' contracts and, despite shipping difficulties and the complaints of planters, he arranged for them to be progressively repatriated without replacement. On the other hand, Logan unilaterally extended the contracts of about 870 Melanesian plantation workers in Western Samoa. Logan's marked antipathy towards Chinese was also based on his conviction that the Samoans deeply resented their presence, and especially the incidence of Chinese cohabitation with Samoan women. In the interests of keeping the Samoan race 'pure', he severely curtailed the civil liberties of the Chinese, taking tough measures to prevent cohabitation or even a Chinese entering a Samoan house.
In the sphere of Samoan affairs Logan was generally content to follow existing German practice. His policy was that Samoan, not European, rights were paramount. Although he lacked his German predecessors' deep knowledge of local custom, and remained somewhat aloof in his relations with Samoan chiefs, native affairs were kept on an even keel, if only by default. One discernible result was a surreptitious revival of some of the practices that the Germans had forbidden the Samoans, such as that of boycotting unpopular local traders. By 1918 Logan was complacently confident that he had won the hearts and minds of the Samoan people in favour of continued empire rule.
If such a sentiment was ever true, it was to change in November 1918 when the pneumonic influenza pandemic was brought to Samoa, from Auckland, by the steamship Talune. Within three weeks some 7,542 Samoans, a staggering 20 per cent, had died. The survivors had no doubt who had let the disaster through the door. Despite the Talune carrying obviously infected passengers, the vessel was not quarantined. By contrast, the governor of neighbouring American Samoa, J. M. Poyer, had promptly quarantined vessels arriving at his islands and so avoided any outbreak. Once ashore the pandemic was completely beyond the ability of Logan's administration to control, not least because freedom of movement went uncurtailed. In this way the disease spread between islands, from Upolu to Savaii.
Under incredible strain, Logan made further misjudgments that contributed to the death toll, such as refusing an offer of medical assistance from American Samoa, thinking that it extended only to the wife of the American consul in Apia rather than to Western Samoa generally. He also made no effort to hide his disgust at the Samoans' apparent lack of will to help themselves, resulting in a round of recrimination that greatly soured Samoan feeling towards New Zealand rule. A commission of inquiry from New Zealand the following year found that Logan had been negligent and the weight of opinion ever since has concurred.
Ironically, the most important years of Logan's life were the least successful. On the basis of a background in local government, but without the benefit of field experience or a grounding in native affairs, he was called on to run a military administration on behalf of Britain. Conscientious and well-meaning, he was also inflexible, unimaginative and somewhat authoritarian. Described as a 'very capable and excellent District Commander' in Auckland, he was thrust by the fortunes of war into a situation that he was ill-equipped either to understand or control. He left Samoa in January 1919. Although he had been appointed CB, and Chevalier de la Légion d'honneur by the French, he was never promoted to brigadier general and came to feel that his military advancement had been sacrificed to the needs of Samoa.
In September 1919 his service with the New Zealand Expeditionary Force ended and he was absorbed into the New Zealand Staff Corps. After being posted to the retired list in December that year, he went to Devonshire, England, where he bought an estate. On the death of his cousin in 1928 he succeeded to the family estates in Lanarkshire, Scotland. In his later years he slid into a somewhat undignified decline, ostentatiously wearing a kilt and readily volunteering the impression that he captured Samoa single-handedly from the Germans. He died at Seaton, Devon, on 4 February 1935, and was buried in the family tomb at Carnwath, Lanarkshire.