"The Sniper" is set during the Irish Civil War, which occurred between 1922 and 1923. In this war, the Irish Republican Army (the "Republicans" in this story) wanted complete independence from England while the Irish Free Staters wanted an independent government for Ireland but to remain part of the British Empire.
The story focuses on one sniper who lies in wait on a rooftop, trying to kill any enemy who crosses his path. The conflict is thus man versus man, particularly when a sniper on an opposing rooftop begins shooting at him. When the sniper shoots at a man in an enemy car and then at a female informant on the street below, he makes his position known to the enemy on the building opposite him. This intensifies the conflict, and the sniper is shot in the arm; the bullet lodges there, rendering his arm virtually useless.
In order to survive, the sniper must determine how to kill the enemy sniper opposite him. He constructs an elaborate plan to make it seem as if he has fallen off the rooftop after being shot; his shooter then exposes himself for a better look at the man he believes he has killed. With a clear target now in view, the sniper shoots his enemy, watching him fall to the ground below in "death agony."
The conflict actually shifts at the end of the story when it becomes clear that clear that the "enemy" the sniper has shot and killed is actually his own brother. This implies the further conflict of man versus self; the sniper will presumably be tormented by his actions once he learns the identity of his victim. Yet this is a harsh truth of civil wars, when lines of alliances are difficult to discern and become inextricably bound to the relationships people have cultivated in a single country.