To determine the symbolism of the moon, one should examine the way different characters react to it. When Policeman Z sees the moon rising as he keeps his watch, it makes him feel lonely and fearful because it means it will soon be dark. The ragged man who approaches the policeman, on the other hand, sings about the moon in a hopeful context, saying at last that he will see the officer again when "we all fall down" at the rising of the moon. In this context, the rising of the moon could be interpreted as a symbol for death or the afterlife. As an older man, Policeman Z does not look forward to his decline, while the ragged man seems accepting of his fate. In light of the historical context of the play, one could also interpret the moon as a symbol of the future change in leadership.
The most obvious setting of the play is in Ireland, as evidenced by the various place names used throughout. At the time the play was written and published, Ireland was still very much under British control. As a representative of English rule, the policemen are at odds with the ragged man, an Irish prisoner of the state who seems like a moral man at heart. One could say that this play predicts the Irish war for independence that began in 1919.
Both the sergeant and the ragged man are common people who arrived at their present circumstances because of chance alone. This is why the sergeant allows the prisoner to escape instead of turning him over to his comrades. The sergeant recognizes himself in the ragged man, noting that their roles could easily have been reversed had the sergeant made different choices. The significance of this, of course, is that the English and Irish are equals, despite the inferiority with which the English treated the Irish at this time in history. Although the policemen is technically Irish, he works on behalf of the English government, thereby treating one his own fellow countrymen in an unfair way.
Policeman B thinks that whoever catches the fugitive will be promoted within the police force. On the other hand, Policeman X says that the public will be furious at whoever captures the wanted man—and maybe even their own family members will condemn them.
A major moment of foreshadowing is when the ragged man sings his song about Granuile. The inciting incident is likely when the ragged man insists on defying Policeman Z's orders. The reversal, of course, is when the ragged man reveals himself to be the fugitive, and Policeman Z very easily lets him escape.