The First World War had an understandable and immediate impact on the lives and works of all contemporary European writers, but Katherine Mansfield's experiences during the war were perhaps more personal and dramatic than those of most of her peers. Having lost her brother, Leslie, who died in a grenade explosion in the war, and having had a stormy love affair in February 1915 with Francis Carco – a French poet and soldier – while illegally travelling to the occupied zone at Grey, Mansfield's existential experiences of loss emerging out of the war throw significant light on the craft and content of her short fiction. Her experience of trauma at the heart of a city is evinced in many accounts. In a letter written to John Middleton Murry on 2 April 1918 from Paris, Mansfield described the visual and auditory effect of gunfire in the street and the grotesque spectacle that followed:

The description underlines the increasing internalisation of trauma and nervous anxiety at the heart of a wartime city. As Mary Burgan argues in an analysis of Mansfield's literary representation of war à propos her personal loss and existential mourning, the wartime horrors ‘actually enabled her to rework the past out of fragments of memory, dreams, and an eventual understanding of the origins of her destabilizing anxieties’. Such modes of representation, with their liminality and psychological intensity, were perhaps best suited to the formal quality of the short story, which can crystallise memory and embodied experiences in episodic and epiphanic narrative frames.

Written in February 1922 during a sojourn at the Victoria Palace hotel in Paris, where Mansfield had gone for X-ray treatment with Dr Ivan Manoukhin, ‘The Fly’ is widely regarded as one of the most psychological representations of repression and loss in First World War fiction, and as a story which also approximates Mansfield's own complex relationship with her father and her response to her brother's death in the war.