Jethro equates the Battle of Antietam with the former Battle of Shiloh because both seem to him to have been empty victories.
In 1861, before the actual battlefield confrontations of the American Civil War had actually begun, warfare had been thought of as something glamorous. To Jethro and a large portion of the untried population,
"War meant loud brass music and shining horses ridden by men wearing uniforms finer than any suit in the stores...when the batle thundered and exploded on all sides - well, some men were killed, of course...(but) it would be shadowy men from distant parts who would die for the pages of future history books" (Chapter 1).
A year later, after the battles of Shiloh, Antietam, and many others, the casualties have become personal and the reality of war has begun to settle into the public consciousness. Jethro's brother Tom has been killed at Shiloh, and a letter full of anguish and disillusionment has just arrived from Shadrach, who has been initiated into battle at Antietam. As the death toll rises with no resolution in sight, Jethro realizes what the population has begun to realize as well - that
"Antietam seem(s) much like Shiloh - a Federal victory in which one (is) hard put to find a step toward final triumph and peace" (Chapter 8).