Oswald was born at Encounter Bay on 27 June 1897, the second of three children to Horace James Sowerby and Elizabeth Ann Sowerby (nee Smith). He was educated at the Victor Harbor public school and on leaving school he took up farming.
The 18-year old farmer enlisted at Adelaide on 8 July 1915, training as a 9th Light Horse Regiment (LHR) reinforcement. He sailed from Melbourne on 27 October 1915 aboard HMAT Ulysses for Egypt, finally reaching the 9th LHR on 28 December 1915. After falling ill in January 1916, Oswald transferred to the 3rd Light Horse Regiment. On 2 March, he was one of 3,000 volunteers to join the newly formed 5th Division Artillery as part of the expansion of the AIF. The existing 18 artillery batteries were increased to 60 in preparation for service on the Western Front. Oswald was assigned to the 59th Battery of the 15th Field Artillery Brigade (FAB).
After training in Egypt, the 15th FAB arrived at Marseilles on 26 June 1916 and moved to northern France where it was issued with 18 pounder field guns from British Army depots. These guns fired fixed one-piece shells weighing 9 Kg (20 pounds) with a maximum range of 6 kilometres (6,525 yards). The guns could fire directly at targets in view but mostly used indirect firing methods to shoot at targets out of sight and shells fired were mainly shrapnel or high explosive. Unfortunately in 1916, shells were often in short supply and many failed to explode until British munitions factories increased production and improved reliability. Successful infantry attacks usually depended on temporarily increasing the number and size of supporting artillery guns to gain local superiority over enemy defences.
On 27 January 1917, Oswald was among 54 men transferred to 18th Battery, 6th Field Artillery Brigade, as it expanded from four to six guns to bring Australian batteries to the same scale as the British Army. This battery was the first South Australian Battery to serve during the war and was placed under command of the 1st ANZAC Corps. Oswald’s Brigade was one of the supporting artillery units during the costly Australian attack at Bullecourt on 10-11 April 1917. On 4 June 1917, Oswald was shell gassed when Australian artillery and working parties in Ploegsteert Wood were heavily shelled for three and half hours. One officer described the effects of that gas as “I was sick – we all were coughing and staggering with our eyes streaming tears”. Evacuated to England five days later, Oswald was unfit to rejoin his Battery at Dickebusch until 15 September 1917.
On 10 February 1918, his Battery was one of twelve supporting a successful infantry raid on enemy trenches near Warneton. Prior to the Battle of Dernancourt in March, his 6th Brigade helped send 90 tons of wool from Ribemont to the rear to avoid it being captured by the advancing German Army. Still at Ribemont in May, Oswald became ill from tonsillitis and diphtheria which caused him to be evacuated to England on 20 May. He remained unfit for duty until October 1918 when he was able to rejoin his unit in France just six weeks before the Armistice. Oswald returned to Australia on the SS Runic and was demobilised on 1 August 1919.
His copy of an 18th Battery commemorative poster hangs in the Victor Harbor RSL. The poster lists places where the Battery saw action, each member’s name together with those who became casualties between 18 October 1916 and 17 October 1917. During the 12 months it fired 62,478 shells, while 53 of its horses became causalities.
Oswald was awarded the 1914-15 Star, the British War Medal and Victory Medal. He married Margaret Graham Donaldson in 1922 and later moved to Perth, Western Australia where he established himself as a public accountant and taxation consultant. Oswald died on 1 December 1978, aged 82. He is buried in the Karrakatta Cemetery, Perth.