Answer: a lot. Like, a whole lot. The following isn’t at all definitive, but it should give you a sense of the historical milieu from which the song came.
I think all of us have a vague idea that “The Battle Hymn of the Republic” has something to do with the Civil War, and you may or may not be aware that its tune is the same as “John Brown’s Body.” a popular song among Union soldiers that they had adapted from an old Methodist revival song, “Say, Brothers, Will You Meet Us.” Wikipedia says this about the origin of the words, taken from an account by a soldier::