This is a harsh, satirical poem that means just the opposite of what it says - so this is an example of "contrast". There is the use of "apostrophe" because the poet addresses three people that are not present, the maiden, the child and the mother - all people who suffer when their "men" are killed by war, and yet, war is kind -- NOT! There is a lot of imagery - for one, there is the image of death, presented by the following:

Because your lover threw wild hands toward the sky
And the affrighted steed ran on alone

We see that the maiden's love died - probably shot, fell off the horse, and the horse ran on.

There is an example of personification:

Hoarse, booming drums of the regiment,

Drums can boom, but they cannot be "hoarse" because they are not human.

There is a metaphor:

Great is the battle-god, great, and his kingdom -
A field where a thousand corpses lie

The "kingdon" of the battle god is the field of battle where thousands lie dead.

Pretty grim, huh?

There is alliteration:

tumbled in the yellow trenches

"tumbled" in the "trenches"

Also, more alliteration:

heart hung humble

You can go through the poem and pick out more images, metaphors, etc.

I HATE this poem because my son is in the Navy, currently deployed, so it is hard to read -- but, that's the point. It evokes emotion, wouldn't you agree?