Short answers, pulled from the story.
Battle Cry of Freedom was written in 1862 by American composer George Frederick Root, who lived from 1820 to 1895. Root composed it during the American Civil War as a patriotic song supporting Unionism and abolitionism.
An estimated 700,000 copies of the sheet music were put in circulation. The demand was so high that the music publisher ran 14 printing presses simultaneously and still could not keep up.
A modified Union version served as the campaign song for the Lincoln-Johnson ticket in the 1864 presidential election. It was also used in the 1880 presidential election campaign for James Garfield.
Yes. Composer H. L. Schreiner and lyricist W. H. Barnes adapted the song for Confederate use during the Civil War, repurposing Root's melody and structure for the Southern cause.
Gottschalk wrote in his diary that he thought Battle Cry of Freedom "should be our national anthem." He composed a concert paraphrase for solo piano based on it in 1863, titled "Le Cri de delivrance," opus 55, and dedicated it to Root, who was a personal friend.
The song unified soldiers from both the abolitionist and unionist wings of the Northern cause because its lyrics were deliberately open-ended. Union veteran Henry Stone recalled that it ran through army camps like wildfire and put as much spirit into the men as a victory in battle.