The setting of the short story "The Sniper" is the Irish Civil War, a conflict between the Irish Republican Army (IRA, the army of the Irish Republic) and the British security forces in Ireland. This war for Irish independence lasted over two years. Certainly, civil wars such as this one have sometimes pitted families against families, and brother against brother, and this is the case in Liam O'Flaherty's stunning short story.
Here is how the plot is arranged in "The Sniper" (the words in bold are the key points):
There is very little exposition in this story. The reader simply reads that the city of Dublin, Ireland, "lay enveloped in darkness but for the dim light of the moon," and in the early morning the reports of machine guns and rifles are heard. On the top of the roof of some building near O'Connell Bridge lies a young man who is a Republican sniper; he is quietly watching and listening.
This Irish Republican sniper is engaged in war with those who support English rule in Ireland. After having a sandwich and a couple of swallows of whisky, the young soldier craves a cigarette. He debates whether he should light a match as the spark may be seen, but he gives in to his desire. When he does so, a bullet "whizzed" over his head. Quickly, he puts out the cigarette and tries to discover from where the bullet has come.
Then, this sniper sees that a woman on the street who stands by an armored vehicle points up to the roof where he is. A bullet tears into his arm, fracturing the bone. He knows that he must do something to flush out the sniper on the other building. So, he places his cap on the end of his rifle and waves it. Then, he lets his rifle drop so that the other sniper will think that he has fallen off the roof. His plan works because the other soldier stands and looks across as his head is "silhouetted against the sky."
The wounded sniper takes as steady an aim as he can.
His hand trembled with eagerness. Pressing his lips together, he took a deep breath through his nostrils and fired. He was almost deafened with the report and his arm shook with the recoil.... His enemy had been hit.
The dying man doubles over and tumbles through the air and lands in the street with a dull thud. Watching this, the sniper loses the "lust of battle" and feels remorse.
He revolted from the sight of the shattered mass of his dead enemy. His teeth chattered, he began to gibber to himself, cursing the war, cursing himself, cursing everybody.
The sniper decides to meet with his company commander, so he climbs down from the top of the building.
Once in the street, the sniper feels a curiosity about the identity of the man he has shot. He risks going over to see him since the shooting is not near him. He dashes across the street.
A machine gun tore up the ground around him with a hail of bullets, but he escaped. He threw himself face downward beside the corpse.
When the machine gun stops, the sniper turns the body over and finds himself looking at the face of his own brother.