The lyrics to When Johnny Comes Marching Home were written by the Irish-American bandleade. The story of "When Johnny comes Marching Home" is also the story of Patrick Sarsfield Gilmore. Gilmore, an 1848 Irish immigrant to Boston, was considered by no less a musician than John Philip Sousa as the "Father of the American Band." Johnny is a boy the went to the war when he was little and fought for the north. The song is based on the civil war on a boy named Johnny. More than 3 million men and boys fought against their countrymen in the Civil War, and more than 620,000 lost their lives -- 2 percent of the U.S. population. When Johnny went to go fight in the wr f