Keith Lindsay Stewart was born at Timaru on 30 December 1896, the son of David Stewart, a bank manager, and his wife, Charlotte Maud Fuller. He attended Napier Boys’ High School from 1905 to 1911 and Wanganui Collegiate School from 1912 to 1914, before successfully applying for admission to the Royal Military College of Australia at Duntroon, which he entered on 12 March 1914. He had a pronounced stutter.
Stewart graduated early in April 1916 to join the New Zealand Expeditionary Force, but did not leave New Zealand until 7 June 1917. In September he became adjutant of the New Zealand Training Units and Depots in Egypt, in which capacity he served until December 1918. He was later posted to the headquarters of the Australian and New Zealand Mounted Division, and was made an MBE for his service in Egypt. On his arrival back in New Zealand in December 1919 he resumed his career in the New Zealand Staff Corps, initially as staff officer to the general officer commanding the New Zealand military forces. On 5 September 1922 he married Rita Florence Moss at Wellington; they would have a son and a daughter.
After serving as a staff officer in Palmerston North, Stewart went to Britain to attend a two-year course at the Staff College at Camberley. Having successfully completed this course, he attended another, before returning to New Zealand in September 1930. Soon afterwards he was appointed as staff officer in the Ceylon Defence Force, but was disappointed to find his duties initially below his training. He managed to extend his role, however, and eventually completed a congenial and professionally valuable posting. Described as ‘an officer of sound judgement, tact and general ability of a high order’, he was made an OBE for his services.
Following his return to New Zealand in October 1934, Stewart was posted to Dunedin, where he served as brigade major of the 3rd Mounted Rifles Brigade and as staff officer in charge of the local regimental district, again drawing consistently favourable reports from his superiors. In 1937 he became general staff officer in the headquarters of Southern Command in Christchurch. On the outbreak of the Second World War he was immediately called to Wellington as general staff officer (training and staff duties) at Army Headquarters.
Posted to 2NZEF, Stewart left New Zealand with the 1st Echelon on 5 January 1940. Until 20 October 1941 he was a senior staff officer in the headquarters of 2nd New Zealand Division. During the battle of Crete he served, with the rank of brigadier, as the chief staff officer in the headquarters of the commander of the Allied forces on the island, Major General B. C. Freyberg. These services earned him a mention in dispatches and appointment as a DSO. With his health impaired, he returned to New Zealand at the end of 1941 to become deputy chief of the general staff.
In July 1943 Stewart returned to the Middle East, where he assumed command of 5th New Zealand Infantry Brigade. Between November 1943 and March 1944 he commanded 4th New Zealand Armoured Brigade, before returning to 5th Brigade. For this service he would later be again mentioned in dispatches. On 1 August 1944, while making a reconnaissance of forward positions, he was taken prisoner of war. He was held in Germany until liberated in March 1945. During the brief period before the arrival of Allied forces, he assumed control of the town of Giessen. By July 1945, with his hopes of finding another position with 2NZEF dashed, he was back in New Zealand, where he was made a CBE. Appointed to command the New Zealand troops who were to take part in the Allied occupation of Japan, he returned to the Middle East yet again in October 1945 to take command of 9th New Zealand Infantry Brigade, and proceeded with it to Japan in early 1946. Stewart’s war service, for which he was awarded the Greek Military Cross and made an officer in the US Legion of Merit, ended with his relief in July 1946.
Stewart resumed his regular career in Wellington on 1 September 1946 as adjutant general and second military member of the Army Board. He was appointed a CB in 1947. On 1 April 1949 he became chief of the general staff and first military member. He was also commander of the New Zealand Division. Stewart was heavily involved in the development of plans for the dispatch of a new expeditionary force to the Middle East should war break out with the Soviet Union. During 1950 he became embroiled in a dispute with the prime minister, Sidney Holland, over the urgency with which these plans should be advanced in the existing international situation. Holland objected to Stewart’s attempts to pressure his government into a rapid decision. Relations were restored after Stewart apologised, and he and Holland co-operated amicably over the development of a New Zealand response to the crisis which erupted in Korea in June 1950.
Holland’s antipathetic feelings probably account for his government’s failure to follow precedent in awarding Stewart a knighthood when he relinquished his posts on 31 March 1952. It was not until 1958, under a Labour administration, that Stewart was appointed a KBE.
In retirement Stewart took up residence in Kerikeri. Posted to the retired list in 1954, he served as colonel of the lst Armoured Regiment until 1959. He died at Kawakawa on 13 November 1972, survived by his wife and children.