In "War is Kind," Crane focuses on the mental torment faced by dying soldiers and their families, rather than celebrating their heroic or patriotic deeds. His goal is to portray the world as he sees it, not as he wishes it to be. Much of Crane's poetry and fiction examine human behavior in extreme situations, whether it's the hardships of the poor on New York City's streets, the interactions of men in a lifeboat threatened by drowning, or the actions of soldiers under heavy fire. His deterministic viewpoint, a key aspect of naturalism, is evident in his vivid portrayals of soldiers' deaths. They die alone, frightened, and angry, in fields "where a thousand corpses lie." Unlike some of his prose that seeks to depict humanity with a more objective, scientific lens, "War is Kind" also delivers a moral critique of the alleged "naturalness" of war. The speaker subtly mocks the regiment that trains soldiers "to drill and die" and "Point[s] for them the virtue of slaughter." This critique suggests that Crane, at least in this piece, believes things could be different. While he empathizes with the plight of the dying, he criticizes the institutions that promote war, especially the military, symbolized by the regiment that "make[s] plain ... [to the soldiers] the excellence of killing." Crane expresses this criticism through his bitterly ironic refrain that "war is kind."

"War is Kind" subtly questions the validity and impact of patriotism, both as a mindset and as a belief system. The flag, representing national pride and called "the unexplained glory" by the speaker, flies over soldiers as they march to their deaths on the battlefield. This notion of "unexplainedness" highlights the speaker's view that there is no logical reason for men to fight and die for a mere symbol. As a representation of national identity and military authority, the flag commands respect. However, Crane depicts it as a symbol of authoritarian power demanding unwavering loyalty. Under this flag, soldiers are taught "the excellence of killing" and "the virtue of slaughter." By attributing such dark motives to a nation, the idea is reinforced that patriotism involves not only blind obedience but also a lack of critical examination of what loyalty to one's country truly entails.

Crane underscores this idea by suggesting that those loyal to the flag "were born to drill and die," indicating they had no other choice. In Crane's time, patriotism was a compelling force, much like it is today. In its extreme and public forms, it fosters an almost militaristic devotion to a nation's decisions, regardless of their morality. For example, during the Vietnam War, many Americans criticized Jane Fonda when she publicly questioned the United States' involvement. However, Fonda claimed she was acting patriotically because she desired her country to make morally sound decisions. Crane portrays the United States as not only sinister but also indifferent and cruel, offering no comfort to those who perished fighting for it.