This song became popular when the war, originally to “preserve the union”, was repackaged in 1863 as a war to wipe out slavery. It’s a propaganda piece of music exploiting religion. Howe takes John Brown’s Baby music and write new anti South agitprop piece turning the Civil War into a religious war. Brilliant.
Nothing "anti-South" about it, but certainly Howe's song puts the lie to our pro-Confederates' claim that Civil War was "not about slavery".
As for "religious war", well... people who are ignorant of the Bible sometimes claim it supports slavery.
It does not.
At most it tolerates slavery where lawful, but not for God's people.
That's what Exodus & Jeremiah 34 is all about.
Why did Judah fall to the Babylonians?
For the same reason the South fell to the United States.
Read it and weep.
And did you note she was the daughter of a Wall Street Banker? Funny that.