As I explained it was originally used in the Civil War and the language was oriented to be against the Confederacy, "the republic", "one nation, indivisible". It was first used in the schools in 1892. "Under God" was added in 1954 and ealier in the Cold War. I am not sure when it was first widely used in the schools. It may have been in WWII or early Cold War, but I think before 1954.