Until the early 19th century, warfare was generally restricted to fighting between professional armies that did not involve civilian populations. (Yes, there will be exceptions for guerrilla fighting and insurrections, such as the American Revolution in which civilians got caught up.) But the unfortunate fact is that warfare worldwide, since the late stages of the Civil War, have involved civilian populations to one extent of another, in which civilians, infrastructure, and sources of supply become military targets. Sherman was simply an early practitioner of this type of warfare, albeit in a much milder form than what we have since become accustomed to.