The text which comes from a song called "Bombed Last Night" and is one example of the many Trench Songs sung by soldiers during the second World War.
A theme in literature, or song, defines a text's message or moral. Therefore, this excerpt of the song shows the horror the soldiers of World War II felt.
Without question, the soldiers are fearful (and rightly so) based upon the fact that they have been bombed in the past and are sure they will be bombed in the future. They are sure, as denoted by "going to get bombed tonight if we never get bombed any more," showing their fear that they will eventually die.
Not only are the soldiers fearful of the bombings, they are even more fearful of the gassing which have taken place. The soldiers know that the air they are breathing is poisoned and sure to be poisoned further. It seems that the soldiers are simply waiting for the inevitable--death.
Therefore, the theme of the text speaks to fear. The soldiers are certainly fearful of what has happened and what is to come. The text offers no solitude; instead, only compounds the fears the soldiers surely have.