What "impossible thing" happened after the first battle in The Red Badge of Courage?
Henry's regiment had successfully withstood the first attack by the Confederates, and the raw recruits celebrated what they perceived to be a victory in their first action.
So it was all over at last! The supreme trial had been passed. The red, formidable difficulties of war had been vanquished.
He went into an ecstasy of self-satisfaction... He perceived that the man who had fought thus was magnificent. (Chapter VI)
To the inexperienced soldiers, their day was done: The enemy had retreated, and Henry's comrades quickly became convinced of their invincibility. Some of them even took to relaxing, sprawling out "luxuriously on the ground" and sharing handshakes for what they believed was a battle won. But the first Confederate attack was only part of the feeling-out process, an initial probe to determine the strength of their enemy. They soon formed again, in larger numbers, and when
The youth turned quick eyes upon the field... forms begin to swell in masses out of a distant wood. He again saw the tilted flag speeding forward. (Chapter VI)
The confident Union troops suddenly questioned their own bravery, and they wondered if they could withstand another such frontal assault. They quickly reverted to "dejection," and saw the oncoming foe as "machines of steel... an onslaught of redoubtable dragons." To Henry, the sudden change of events was unthinkable.
The youth stared. Surely, he thought, this impossible thing was not about to happen. He waited as if he expected the enemy to suddenly stop, apologize, and retire bowing. It was all a mistake. (Chapter VI)
Although Henry had stood his ground during the first attack--he had not run as he feared he might--he wondered if he could withstand another charge. "There was a great uncertainty about his knee joints," and his greatest fear was soon realized: He turned and "ran like a rabbit... a proverbial chicken."