Well, the point here is military THEORY. Sherman and Sheridan were the first, in modern times to carry out a military theory of deliberately targetting civil populations, as opposed to the earlier idea of the objective of war being to destroy the enemy’s army and capture his strongholds.
Suggest you review the history of the Vendee's revolt against the French Revolution.
http://en.wikipedia.org/wiki/Revolt_in_the_Vend%C3%A9e#Accusation_of_genocide
Or the Sullivan Expedition ordered by George Washington during our Revolution.
http://en.wikipedia.org/wiki/Sullivan_Expedition
Or the Peninsular War.
http://books.google.com/books?id=3huwPLzjzYYC&pg=PA244&lpg=PA244&dq=peninsular+war+atrocities&source=bl&ots=ZyB6_VsdhB&sig=lH85d-fnOFBWI7RjUAXlAjTJ3EU&hl=en&ei=aoB8TqqcK8-utweJt7ls&sa=X&oi=book_result&ct=result&resnum=5&ved=0CDkQ6AEwBA#v=onepage&q=peninsular%20war%20atrocities&f=false