Crane in his various works seems to present war with gritty realism. He explores such concepts as heroism and patriotism and profoundly questions the extent to which traditional notions of these concepts are accurate and even useful. Consider how ironic he is about war in his poem "War is Kind," which features lines such as:
These men were born to drill and die.
Point for them the virture of slaughter,
Make plain to them the excellence of killing
And a field where a thousand corpses lie.
Note how these lines bitterly compare to the title of the poem. Crane seems determined to debunk the various myths surrounding war and the glory and honour associated with it.
Likewise in some of his shorter fiction, such as "A Mystery of Heroism," similar problems are raised. In this story, Private Collins shows incredible bravery in going and getting water across a field directly under the fire of the opposing army's guns. Yet, in spite of being successful, this water is spilt when two officers fight over it, pointing towards the futility of war and man's involvement in it.
Personally, although I have (fortunately) never been in a war, I find lots of truth in Crane's view. Ignoring the harsh realities of war allows myths to be created and sustained that say nothing of the bleak, futile suffering of so many soldiers whose lives are extinguished.