The Red Badge of Courage conveys a negative tone through most of the novella, but it does shift throughout the various chapters. It begins ominous, and wherever a battle scene is described, a tone of morbid excitement is created. It is not until the very end of the story that the tone becomes hopeful.
At the beginning of the story, the tone is ominous:
The cold passed reluctantly from the earth, and the retiring fogs revealed an army stretched out on the hills, resting. As the landscape changed from brown to green, the army awakened, and began to tremble with eagerness at the noise of rumors. It cast its eyes upon the roads, which were growing from long troughs of liquid mud to proper thoroughfares. A river, amber-tinted in the shadow of its banks, purled at the army's feet; and at night, when the stream had become of a sorrowful blackness, one could see across it the red, eye-like gleam of hostile camp-fires set in the low brows of distant hills.
In this opening description of setting, the reader is given a picture of danger lurking ahead. While the army is awakening from a rest, the rumor of an impending battle begins to circulate. The army seems to be looking out for signs of danger, which is why it "cast[s] its eyes upon the roads." Eminent danger is also present in the description of the "shadow" of the river at the army's feet and the "blackness" in the distance, where fires burn like "red . . . hostile" eyes. This description of danger makes the youth's naive excitement over serving in battle seem foolish.
Henry's mother's reaction further reinforces the folly of the youth by adding to the ominous tone. A sense of foreboding is present in how solemnly she gives her son advice for the days ahead. She says that when the time comes for Henry to do his duty in battle, he must not let guilt over what he might be forced to do for his own survival hinder him. She knows that war will make a beast of her son, and that becoming part of the brutal war machine will be his best chance of survival. She says, "If so be a time comes when yeh have to be kilt or do a mean thing, why, Henry, don't think of anything 'cept what's right . . . the Lord 'll take keer of us all." Her attention to her son's emotions and soul in light of the experiences that lay ahead of him further cultivate the ominous tone of this first chapter.
When Henry is in battle, the tone becomes one of morbid excitement, as images are employed to create an environment of survival of the fittest. This dark excitement is also present in how beastly the soldiers become in their war-time environment. For example, where Henry faces battle in Chapter 5, the text reads:
Presently he began to feel the effects of the war atmosphere—a blistering sweat, a sensation that his eyeballs were about to crack like hot stones. A burning roar filled his ears.
Following this came a red rage. He developed the acute exasperation of a pestered animal, a well-meaning cow worried by dogs. He had a mad feeling against his rifle, which could only be used against one life at a time. He wished to rush forward and strangle with his fingers. He craved a power that would enable him to make a world-sweeping gesture and brush all back. His impotency appeared to him, and made his rage into that of a driven beast.
Imagery is present in the texture of "blistering sweat" and the heat of his eyes, as well as the "roar filling his ears." Imagery places the reader in the midst of the dangerous, brutal environment that Henry is experiencing in this section. The danger is changing him into a sort of wild, blood-thirsty animal. A tone of morbid excitement is further cultivated by the descriptions of his impatience to "rush forward and strangle with his fingers." Hyperbole adds to morbidity, because Henry feels he could "brush back"—or kill—masses of individuals coming to battle against him, as his rage is so immense.
At the end of the story, when Henry is outside of a battle environment, the tone turns markedly hopeful. This is partly because the youth has earned his "red badge of courage" and proven himself a man. But the change in tone is also due to Stephen Crane being a naturalism author. He used tone to create mood appropriate for the environment in which the protagonist found himself. When he was heading into battle and in the midst of battle, the tone had to be negative, because the act of war brings violence, bloodshed, wounds, death, loss, fear, guilt, etc. But as Henry leaves battle, and returns to a less dangerous environment, the story changes to create a mood more appropriate for times of peace:
Yet the youth smiled, for he saw that the world was a world for him, though many discovered it to be made of oaths and walking sticks. He had rid himself of the red sickness of battle. The sultry nightmare was in the past. He had been an animal blistered and sweating in the heat and pain of war. He turned now with a lover's thirst to images of tranquil skies, fresh meadows, cool brooks—an existence of soft and eternal peace.
Over the river a golden ray of sun came through the hosts of leaden rain clouds.
Henry Fleming is no longer an "animal," acting on his animal instincts in an environment of danger. Now he is a "man" free from the "red sickness of battle." The setting, too, is far from ominous. It has turned hopeful, with light breaking through clouds of rain.