What is the theme in The Sniper by Liam O'Flaherty?

The complementary themes of civil war and warfare are the most obvious in "The Sniper." The story takes as its setting Dublin, Ireland, during the Irish civil war. The fighting began in 1922, after the Irish Parliament voted to accept the Anglo-Irish Treaty dividing the island of Ireland into northern and southern parts. Before the treaty, Irish nationalists had united against the British, their common foe, or against Northern Irish Protestants who supported union with England. After the treaty was signed, however, Irish aggression was turned inward. Over the next few years, the Irish people remained bitterly split, and some took up arms against their friends, family members, and countrymen.