Interestingly, the author of this play wrote a number of plays featuring Irish peasants, but she herself insisted that these were not overtly political works, but the title refers to a popular Irish ballad where the "rising" of the moon refers to the "rising" of the powers in revolt, which contradicts her so-called peaceful intentions in writing this play. Clearly, this play acts as a pageant of all the sorrows that Ireland suffered thanks to English rule. Note the high number of traditional Irish ballads that are shared by the Ragged Man and the Sergeant. In particular, the play draws attention explicitly to one such song, where Granuaile, the old and suffering woman in the ballad, is a symbol of Ireland. The Ragged Man omits the last line of this song, which the Sergeant fills in for him: "Her gown she wore was stained with gore." Such an obvious reference to Irish martyrs and those who had shed blood as a result of resisting English rule certainly led to the authorities believing this was a subversive work.
Such a backdrop to this play highlights its theme of individual choice in response to political realities. The character of the Sergeant is key in this respect: as the moonlight impacts his character, he is forced to consider his identity as an officer in the pay of the English or an Irish sympathiser. The play suggests that there is no middle road, and you either stand with the oppressors or against them. The way in which the Sergeant is left by himself at the end of the play, puzzling over who he is, supports this theme of personal responsibility in the face of armed rule.
The theme of this play is the same as the title of a song the ragged man sings - "Rising of the Moon".
The ragged man tells sergeant that had he not joined the force, he could have been a rebel for cause of ireland because sergeant was also from ireland and its obvious that he hasnt forgotten his roots.
Sergeant passes up the chance for what he considers a better cause.