What is the theme of the story Episode of War Stephen Crane?

sarcasm

The poem is ironic.

The losses of war are depicted in the three main stanzas, highlighting the loss, fear and pain that comes from war... and the two choruses first suggest the glory of war but end in an ironic tone.?

Crane is trying to show the futility of war by saying it is kind while it all it actually does is cause hurt, pain and suffering.

The lines "virtue of slaughter" and "Excellence of killing" are both ironic and oxymoronic. As is the line "Great is the battle god, great, and his kingdom/A field where a thousand corpses lie" - Crane does not mean this literally, his repetition puts heavy emphasis on the great, and suggesting the kingdom of war is inhabited only by the dead clearly shows that you should not take this statement in a literal manner.