Stephen Charles Allen was born in the Sydney suburb of Balmain in 1891. The 23-year-old carter enlisted with the Australian Imperial Force on 18 July 1915. His brother Robert had enlisted just over a week earlier. Both brothers departed Sydney with reinforcements for the 13th Infantry Battalion aboard HMAT Ballarat on 6 September 1915.

The following June, Allen and his brother arrived on the Western Front with other men of the 13th Battalion. In letters home to his mother and sister he wrote that he was glad to have left Egypt and described the incessant rain at the front. In one letter to his sister Allen included a preserved poppy. He was with the 13th Battalion when the unit fought in its first major actions at Pozières and at nearby Mouquet Farm in July and August 1916. On 14 August, in the midst of the fighting around Mouquet Farm, both Allen brothers failed to report back in after fatigue duty. Initially listed as missing in action, a court of inquiry found that the two brothers had been killed in action by the same artillery shell, close to the front line. Stephen Charles Allen is commemorated on the Villers-Bretonneux Memorial in France.