Robert Beattie Allen was born in the Sydney suburb of Balmain in 1888. As a 27-year-old labourer he enlisted with the Australian Imperial Force on 9 July 1915. His brother Stephen enlisted just over a week later, and both brothers departed Sydney with reinforcements for the 13th Infantry Battalion aboard HMAT Ballarat on 6 September 1915.

The following June the two men arrived on the Western Front with other members of the 13th Battalion. Despite the circumstances, Allen remembered to send a birthday card to his sister half a world away back in Australia. The battalion 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 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. Robert Beattie Allen is commemorated on the Villers-Bretonneux Memorial in France.