What is the external conflict in "The Sniper"?

The central conflict is set against the larger struggles of the Irish Civil War, which came after Irish republicans launched an armed uprising against British rule and proclaimed the Irish Republic. It is this civil war between Irish Catholic and Irish Protestants that is the setting of "The Sniper." A sniper for the Irish Republic is the protagonist. He is on the roof of a building, and he fights against another sniper who is on the other political side. This battle is the main conflict of the story.
In 1922, Ireland was partitioned under British law by the Government of Ireland Act, an act which created Northern Ireland. However, not long after this division of Ireland, political and sectarian violence broke out between republicans (Catholics) and loyalists (Protestants). This civil war, called the Irish War of Independence, continued for eleven months. The protagonist and titular character of the sniper is part of this fight to remove the British from Ireland. When he is shot by the sniper who has aligned himself with the British rule of northern Ireland, the protagonist struggles to retaliate against this sniper in his effort to survive. Through his clever plan, the protagonist tricks the other sniper and is then able to shoot and kill this other man. Tragically, when he arrives on the street where the dead man lies, the protagonist discovers that he has shot his brother.

The main external conflict in "The Sniper" is the sniper's battle to stay alive.  This conflict involves multiple parts.  The conflict begins when the sniper lights his cigarette and gives his position away to the Free Stater sniper.  From this moment forward, the Republican sniper is in a battle for his life.  The enemy knows his location, and he must eliminate everybody that knows his location.  An old woman on the street flags down a soldier in an armored vehicle, and she points up to the sniper's location.  If the sniper doesn't kill those two on the street, then reinforcements can be called to his location.  Under fire from the other sniper, the protagonist successfully kills the old woman and the soldier.  The sniper then uses some trickery to kill the enemy sniper.  
Another external conflict that exists in the story is the war itself.  It is a civil war between the Irish Republicans and the Irish Free Staters.