the five senses of sight, sound, taste, smell, and touch.

Imagery, which shows rather than tells, is a powerful way of telling a story. Crane uses such images as

your lover threw wild hands toward the sky [as he died] [...]
A field where a thousand corpses lie

and

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

juxtaposed against the empty statement "war is kind" to show that war is anything but kind.

The ironized juxtaposition occurs on a more granular level as well: the word "virtue" is placed near "slaughter," and "excellence" is placed near "killing." We read of the "splendid shroud of your son," and the words splendid and shroud create a jarring juxtaposition of a positive adjective and a negative image, for a shroud is a cloth that wraps around a dead body.

Crane also uses the poetic device of alliteration in the line "splendid shroud of your son," repeating the "s" sound three times at the beginning of words, which puts the emphasis on splendid, shroud, and son. This again highlights the irony: no parent of a son is likely to find his shroud splendid. Crane employs alliteration again in the ironic: "Great is the battle-god, great [...]" and in "weep" and "war" in the refrain.

Crane's poem “War is Kind” shows a deep understanding of those who are left behind when a solider fights a war.  First of all, there is irony.  The title uses irony, because war is not really kind.  It is a relief that a solider dies to end his suffering, but war is not literally kind.  

Another feature of almost all of Crane’s writing, especially the war works, is the detailed imagery.  Crane describes a “field where a thousand corpses lie” (line 11), a soldier who “threw wild hands toward the sky” (line 2), “yellow trenches” (line 13) and the “swift blazing flag of the regiment,/Eagle with crest of red and gold” (line 17-18).

Hoarse, booming drums of the regiment,
     Little souls who thirst for fight,
     These men were born to drill and die. (enotes etext)

The sensory details allow you to hear the drums booming, while the figurative language drives the point home.  The personification of souls, especially calling them “little,” makes the scene not just real but sentimental.  Figurative language is also used throughout the poem, to make concepts larger than life.

Mother whose heart hung humble as a button
On the bright splendid shroud of your son (line 23-24).

The similes used in these two lines appeal to our emotions, and direct us to feel as the poet feels- joyous images (“bright splendid”) are juxtaposed with melancholy ones (“hear hung humble as a button” and “shroud”).  This purposefully creates Crane's paradoxical view of war as both terrible and ironically kind.

Stephen Crane calls war "kind" because he mocks with bitter irony the chauvinism that would have young men believe that going to war is noble and dying for one's country is heroic.

For those in the military, Crane ironically declares that they are meant for death:

These men were born to drill and die.
The unexplained glory flies above them,
Great is the Battle-God, great, and his Kingdom--
A field where a thousand corpses lie.

As a writer of the Naturalist school of thought, Crane takes a rather deterministic view of the dying of soldiers in stanza 4 as he points to the "virtue of slaughter" and "the excellence of killing," satirically implying that since the soldiers are destined to die, war accomplishes mass deaths and is an efficient way to end many lives.
Thus, the reader perceives that Crane really feels that war is anything but "kind"; it is an outrage against the youth of soldiers, stealing them from their mothers and lovers, only to be buried in "A field where a thousand corpses lie."  

The poem, published in 1899 by Stephen Crane, speaks ironically and points out the cruelty of war. Stanzas one, three, and five are written in second person, each addressing a different woman who has lost a loved one in battle. In the first stanza, a maiden who has lost her lover is told not to weep because war is kind. The picture of the woman's lover raising his hands and falling off the horse in death depicts war in the era of horse-mounted cavalry. The command to not weep is ironic because, of course, the woman will not be able to stop her tears. The statement that war is kind is verbal irony; it is clear that war has not been kind to the woman or to the fallen soldier.

The third stanza tells a daughter ('babe") not to weep because her father perished in "the yellow trenches." Although this could simply be a reference to the color of the sandy soil soldiers dug their trenches in, it could also allude to yellow fever, which killed more American soldiers during the Spanish Civil War than fighting did. (Crane had covered the war as a journalist and contracted yellow fever himself in Cuba in 1898.) Again, the command not to weep and the statement that war is kind are ironic.

The final stanza tells a mother not to weep for her fallen son. 

The second and fourth stanzas are indented and use a different voice. While the other stanzas seem somewhat sympathetic to the women grieving their lost loved ones, these stanzas seem to fully embrace the military effort and the way it takes advantage of its men. Crane's poetry often used two contrasting voices that taken together produce an overall message. Here the indented stanzas form a type of Chorus that iterates the outlook of the military system, which considers its soldiers "little souls" and "men [who] were born to drill and die." These stanzas use hyperbole to overstate the attitude of the military: "Great is the battle god," and "Point for them the virtue of slaughter, / Make plain to them the excellence of killing." By juxtaposing these stanzas that represent the view of the armed services with the stanzas that focus in on the pain and suffering that war causes to individuals, Crane creates an even stronger negative emotion toward war. 

Stephen Crane, who was a war correspondent and saw the war victims and battles in all their carnage, writes with a satirical tone that employs bitter irony to underscore the senseless brutality and suffering of war. Certainly, in the second stanza Crane satirizes the chauvinistic propaganda about "battle-god(s)" and the "glory" of war with verbal irony:

Hoarse, booming drums of the regiment,
Little souls who thirst for a fight,
These men were born to drill and die.
The unexplained glory flies above them,
Great is the battle-god, great, and his kingdom

Of course, there is anything but "glory" in these men's dying since men are not really born to be soldiers. There is no "battle-god," nor can he have a kingdom, and battle, in which lives are lost that is "great".

Indeed, the satirical tone of this poem prevails throughout the verses. For instance, the speaker tells the child, "babe," not to weep because his father "Raged at his breast, gulped and died"; further, he tells the mother whose heart "hung humble as a button" on the "splendid shroud" of her son that she also should not weep since "war is kind."

The poem "War Is Kind" presents the horrors of war through its powerful and graphic imagery, while continually repeating the verbal irony "War is kind" to show the ways we try to lie to ourselves about war and its true consequences.

In the opening stanza, the poem's speaker urges the grieving maiden, "Do not weep," despite the fact that her "lover threw wild hands/toward the sky/and the affrighted steed ran on alone."  This is a grim posture of death, but we are supposed to believe, as the second stanza states:

Hoarse, booming drums of the regiment
Little souls who thirst for fight,
These men were born to drill and die.
The unexplained glory flies above them.
Great is the battle-god, great, and is kingdom--
A field where a thousand corpses lie.

This infers that men should be proud to die in service to their countries - this is what they were born for - and women should be glad to give up their sons, lovers, and husbands to such a glorious cause.  However, the irony of the words "War is kind" keeps coming back, leading the reader to conclude that this is not truly how the author feels or what he believes.

In the third stanza, the speaker tells the babe that neither should he weep,  though his "father tumbles/in the yellow trnches" and though he "raged ... gulped and died" in his final moments.  He died, presumably, a hero - and therefore, his family should not weep.  They should, instead, be proud of his sacrifice.

The fourth stanza repeats the idea that "these men were born to drill and die," this time expanding on the idea, saying that there is "virtue" in slaughter and "excellence" in killing - though, the final image of "a field where a thousand corpses lie" again leads the reader to conclude that war is a horrendous and terrible act.

The final stanza addresses the "Mother whose heart (hangs) humble as a button/on the bright splendid shroud of (her son)."   This final image shows the epitome of grief, as a mother cries over her dead son, having to say goodbye to the child she bore, the son she raised, the man on whom her hopes rested.  War is not truly kind - it steals joy, security, peace, and loved ones.