What is the irony in this passage?

6- The two enemies stood glaring at one another for a long silent moment. Each had a rifle in his hand, each had hate in his heart and murder uppermost in his mind. The chance had come to give full play to the passions of a lifetime. But a man who has been brought up under the code of a restraining civilisation cannot easily nerve himself to shoot down his neighbour in cold blood and without word spoken, except for an offence against his hearth and honour.
A. Each man had planned to kill the other, but when they came face to face, they hesitated.
B. Georg was hiding behind the tree to surprise Urlich.
C. The night was going to get darker.