Why do soldiers pose for photographs with hands in shirt?

Answer 1

I'll bet you've been looking at old U.S. Civil War era photographs. So far as I know, it was just a convention of the period, much as men today will often pose with their hands in their pockets. (U.S. Grant often had one hand in his pocket and the other in his shirt. His wife Julia said that was just how he liked to look, even when President.) The main thing was to have the hands occupied with something. Notice how often Civil War soldiers posed with their weapons. Aside from wanting to look fierce and aggressive, it gave them something to do with their hands.

Hands are something of a nuisance, especially when you suddenly become conscious of them. Most of the time you're not thinking about them, but when you are, they become these huge hams on the ends of your arms. Good portrait photographers become expert, not just at posing the head and body, but at posing the hands as well. Nowadays we would resist having a subject pose with his hand in his shirt because it would make the photo look dated, but we might have a man thrust one hand in a pocket or hold his lapel in order to have his hands doing something. A favorite trick of mine with people who wore eyeglasses was to take them off and have the subject hold the glasses folded in one hand. This solved two issues: the hand was occupied, and I didn't have to deal with reflections and distortions of the face from the glasses.