I particularly like the descriptions of the first battle (encompassing Chapters 4-6) of Stephen Crane's The Red Badge of Courage, where The Youth gets his first taste of action before skedaddling in fear after the Confederates reform and attack again. Crane builds the tension slowly over the three chapters, giving vivid descriptions of both the men and their excited dialogue. When Henry's regiment holds off the first Confederate wave, there is relief among the men. They feel that they have proven themselves at last, and that victory is theirs. "The supreme trial had been passed." But when the shout arises, "Here they come ag'in!", the aura about the men reverses, and they wonder if they can withstand another charge from the "machines of steel." When Henry sees some of his fellow comrades turn tail and run, he does the same--an act foreshadowed by his constant worry about how he will react under such circumstances.
(If you haven't seen the old John Huston B&W film version, you should try and find a copy of the video. These chapters come to life beautifully and with the utmost respect to Crane's narrative.)