In his biting antiwar poem “War is Kind,” Crane uses sarcasm to drive home his point about what he sees as the utter futility of human conflict. The very title itself is extremely sarcastic. Although it states that war is kind, it's perfectly clear that the speaker believes the exact opposite. Using the heaviest of heavy irony—which is closely related to sarcasm—Crane leaves us in no doubt about his utter hatred and contempt for war.

Crane's sarcasm is reinforced by the patently ludicrous attempts by the speaker to try and console the young lady whose lover has just been killed on the field of battle. He claims, for instance, that “war is kind” because the young man threw up his frightened hands and fell off his horse. It's difficult to see how anyone can reach such a conclusion; it's a complete non sequitur; it simply doesn't follow from the argument's premises.

If we didn't already from the title, by the time we've reached the end of the first stanza, we can be in no doubt that the poet really does not believe that war is kind or anything like it.

Further evidence of his use of heavy sarcasm to make his point comes in the third stanza, where the speaker tells the dead man's baby not to weep because his father died painfully in a trench.

If this had been a militaristic poem, a poem celebrating the heroism of war, then the speaker would've comforted the dead soldier's family by telling them that he didn't suffer. But instead, he leaves us in no doubt that the man's last few moments on earth were agonizing:

Your father tumbled in the yellow trenches,
Raged at his breast, gulped and died.

And yet, the speaker concludes, this is another example of the kindness of war. Once again, we see the poet resorting to sarcasm to express his feelings about war and all that it represents.