In "The Red Badge of Courage," Stephen Crane explores the concepts of courage, fear, and the complexity of a soldier's experience in battle. If Henry had been captured after a Union loss, his perception of courage would likely be influenced by the societal views on honor and bravery during the Civil War.
Captivity often carried a stigma, and many soldiers—like those Crane describes as having the "shame of captivity"—might have felt that being taken prisoner was a mark of disgrace. If Henry had been captured in such circumstances, he might struggle with feelings of cowardice and failure. Much of Henry's journey throughout the novel revolves around his internal conflict regarding bravery and his initial cowardice during battle.
At the same time, courage is complex and can manifest in various forms. Even in capture, he could argue that he faced a different kind of bravery by enduring the trials of captivity, as well as facing the psychological battle of dealing with his fear and shame. Ultimately, whether he could have considered himself courageous would depend on his personal growth and understanding of what it means to be brave.
In summary, had Henry been captured after a Union loss, he might find it difficult to reconcile his experience with a sense of courage due to societal expectations and his own internal struggles, yet there could also be a deeper recognition of the multifaceted nature of bravery in the face of adversity.