Stewart was born in 1895, part of the Stewart family of Appin in Argyllshire. He was commissioned in the Argyll and Sutherland Highlanders (Princess Louise's) and served inWorld War I. During this war, he was awarded the Military Cross and Bar, and created an Officer of the British Empire (O.B.E.). At the end of the war, Stewart was a Temporary Captain. As with many Army officers between the wars, Stewart was placed on Half Pay, but was restored to Full Pay as a Captain on the 3 June 1925. On the 8 September 1931, Stewart was promoted Major. Stewart's military career was dominated by his service with the Argyll and Sutherland Highlanders, a regiment that he was so wedded to that when he was given command of the 2nd Battalion in the 1930s some of his brother officers did not even realise that he was married with a daughter. He even refused a position at the staff college at Camberley to remain with his battalion thereby losing the only way to senior command.
At the outbreak of the Second World War Stewart was very happily still in command of the 2nd Battalion. Stewart was one of the few British officers to realise the need for training in Jungle warfare that would be necessary in order to defeat the Japanese in a war in Malaya. Due to this obsession with jungle training Stewart earned himself a reputation as a crank amongst the more traditional minded officers of Malaya Command. In early 1941 after his battalion had been transferred from India to Malaya, Stewart began rigorously training his men and developing new tactics to fight in all of the extreme and hostile natural terrain of Malaya. When the 2nd Argylls were thrown into the battle in early December 1941 they were to prove one of the few effective units the Japanese would face in their rapid advance down the peninsular, inflicting heavy casualties in every engagement. Sadly their effectiveness meant that they were continuously used as the buffer and suffered massive casualties as a result.
Stewart was temporarily given command of the Indian 12th Infantry Brigade after Brig.Paris took over the Indian 11th Infantry Division in late December 1941. He was in command of this brigade during the disastrous Battle of Slim River which was where the Argylls suffered their worst casualties. When the Battle of Malaya finally ended and the surviving Allied soldiers retreated across the causeway onto Singapore Island, Stewart and his batman, Drummer Hardy, were the last to cross.
Stewart was soon returned to his beloved Argylls in Singapore after they had been decimated in the fighting on the mainland. The 250 surviving Argylls were reformed with 210Royal Marines, survivors from the H.M.S. Prince of Wales and the H.M.S. Repulse, becoming known as the Plymouth Argylls. Stewart had six days to train the new composite battalion before it was put into action on Singapore Island itself. The Plymouth Argylls suffered heavy casualties during the brief Battle of Singapore. Stewart was evacuated unwillingly from Singapore before its surrender due to the need for experienced officers and men who had proven ability to fight the Japanese Army successfully, an ability rare in the British Army at this time. By the time of the surrender on 15 February the Plymouth Argylls were reduced to 40 officers and men.
What was left of the Plymouth Argyll Battalion, under the command of three captains, were marched into captivity behind their piper. According to some witnesses hundreds of other British Empire soldiers stood to attention as they marched past. Only 52 Argylls managed to escape before Singapore surrendered and make it to Ceylon. Many others were killed or captured when the ships they were escaping on were sunk by Japanese surface and air attack, like Major Angus MacDonald (pictured with Stewart and Sgt.Maj.Munnoch) who died on The Rooseboom.
On the 23 January 1942, Stewart was awarded the Distinguished Service Order (D.S.O.) for his services in the South West Pacific area. He was initially employed as a General Staff Officer Grade 1 in India lecturing on his experiences in Malaya. The need for officers, with jungle warfare experience who had actually fought the Japanese, and seen their tactics was in high demand by the army command in India. Of all the officers to have escaped from Singapore, Stewart, was probably the most experienced. He became the Chief Instructor at the School of Infantry as a Colonel, and later Brigadier General Staff (Training) with 11th Army Group in India. Field Marshall Wavell wrote:
|“||If all units in Malaya had been led with the same foresight and imagination that Brigadier Stewart showed in the training of his battalion, the story of the campaign might have been different. It was the realization of this that led me to order Brigadier Stewart's return to India...to impart his knowledge and ideas to units preparing for the return match with the Japanese.||”|
Stewart's report, written after his arrival in India, and his knowledge along with the knowledge of the other officers who escaped from Singapore, had a direct effect on the training and tactics that would be used by the British and Commonwealth Armies in fighting the Japanese throughout the rest of the war.
Stewart returned to the United Kingdom in early 1945, being given command of the 144 Infantry Brigade on the 19 March 1945. He spent a period as the District Commander for Stirling, the home of the Argyll and Sutherland Highlanders, before retirement on the 13 April 1947.He was a substantive Colonel on retirement, but was awarded the Honorary rank of Brigadier. Stewart wrote the book 'The Thin Red Line, 2nd Argylls in Malaya' (Thomas Nelson, 1947) which was reprinted by the Argyll and Sutherland Regimental Museum. He died on the 14 March 1987 aged 91 years.