"The Hero" is an anti-war poem. Significant literary devices and figures of speech it uses include irony, dialogue, contrast, alliteration, cliche, and imagery to convey the anti-heroic misery of war.

Irony occurs when words or events are the opposite of what we expect. Irony emerges in the first stanza as the mother's dialogue contrasts with her body language to show that the words she says are clichés or cant. The woman says what is expected, such as "We mothers are so proud / Of our dead soldiers," but her body language, in which her "face was bowed," shows the opposite of pride. It is ironic, too, that even the officer bringing the news of the death doesn't believe the rhetoric that the soldiers' deaths in World War I are for a great cause. The soldier's death is depicted as lacking in heroism or any meaning. The line "no one seemed to care" that he died shows in startlingly simple, bitter language the meaningless of the war. This adds a bitter irony to the poem's title.

Imagery also emphasizes the misery of war. The poem uses such everyday language—and such a tone and language of intense weariness—that the images, descriptions using any of the five sense of sight, sound, touch, taste, or smell, jump out powerfully when they occur. We feel the woman's weary sadness in the imagery of her "tired voice" that "quavered" to a "choke." She is so miserable that she chokes on her words rather than cries. Images like "coughed and mumbled" show the officer not as heroic, but as weak and ashamed of the lies he is telling. Finally, in the last stanza, the image of the dead soldier as "swine" is startling in its dehumanizing coldness and anti-heroism. Calling a person a "swine" was a cliche in those days, but it becomes shocking when applied to someone who just died a horrible death.

Alliteration brings added weight to the image of Jack, a "panicked" animal trying to escape slaughter, when Sassoon writes that he is "blown to bits." It is as if the officer is too weary and disillusioned even to grope for a more poetic way to varnish the truth, giving the alliteration a note of raw authenticity.

I'd like to focus on the poem's structure for this answer. In regard to that, some of the poem's literary devices are rhythm, meter, and rhyme.

The rhyme of the poem is not consistent throughout. The first and last stanza are each six lines, and the lines are rhymed in couplet format. The rhyme scheme is AABBCC. The middle stanza is also six lines, but the rhyme scheme changes to ABABCC. When it comes to poetry, words, syllable counts, rhymes, and so on are super important. That shift in rhyme is not random. Different readers might have different ideas about the shift, but I think the shift in rhyme scheme foreshadows the shift in the poem's content. Stanza 1 is all about Jack falling gallantly on the battlefield, and stanza 3 is the truth about Jack. He's a coward. That's a massive shift in Jack's character, and I think the middle stanza's subtle shift in rhyme is meant to shake the reader up a little bit and get us ready for the final stanza's shift in content.

As for rhythm and meter, the poem consistently includes ten syllables per line. It also starts with an iambic rhythm. This would lead a reader to think that the poem is entirely in iambic pentameter. That's a very common rhythm and meter in poetry; however, the poem doesn't stick to it throughout. The poet will occasionally do two unstressed syllables followed by two stressed syllables. This is the case with the first four syllables of line 4:

In the tired voice that quavered to a choke.

This change causes "tired voice" to especially stand out in the line. The change in stressed syllables has a way of jarring the poem. It doesn't read quite as smoothly as it looks like it should. The use of enjambment does this too. Not all lines are end-stopped lines like a lot of poetry readers are used to seeing. Readers have to force themselves to keep reading after certain lines. The enjambment and the syllable changes function in the same way that the change in rhyme scheme functions. They all hint to readers that everything is not exactly as it seems it should be. There is something not "right." The final stanza is the answer to that feeling: Jack is no hero.