It is not known if Oswald ever lived in Stockport, although his father, Francis, lived at 4 Hooper Street, during the War and, probably for some time afterwards, although the records of the War Graves Commission suggest he had returned to Swansea by the early 1920s. The family had originated from Swansea. Oswald was born there and would return to enlist in the army. While still in training, in 1915, he married Adela Bromley in the Nottingham area. They are thought to have set up home, to which Oswald would have returned on leave, in London (after the War, she was living at 476 Upper Richmond Road, Putney).
On 5 September 1915, he went overseas to France with the Battalion but they left the Western Front on 30 October, sailing from Marseilles for the Salonika theatre of the War in Northern Greece, They would now face the Bulgarian Army, However, it would not be the enemy that would cause the greatest loss of life. Conditions for the men were appalling and, for every man killed in action, three would die from disease and illness. Oswald, however, would be one of those killed - no doubt by random enemy shellfire on an otherwise quiet day in trenches.
The Battalion's War Diary, held at the National Archives, records "Work on defences continued. Artillery and machine guns kept up an intermittent fire according to programme on enemy lines and on approaches to their front line. Casualties - 1 O.R. killed." Oswald was unlucky to be the one Other Rank (not an officer) to die.
In November, Francis Thomas arranged for an "In Memoriam" notice to be published in the Stockport Express from a "loving father". It reads,:
There's a lonely grave in Salonika
Where my brave son sleeps
Oft in my eyes tears will come
But I smile to hide the pain