The author develops the idea that spying during the Civil War relied heavily on fieldwork by providing detailed information about the spies and their strategies. This highlights the critical role of human elements in intelligence-gathering despite technological advances. Fieldwork is presented as a blend of bravery and skill that was essential for success. ;
The author develops the central idea that spying during the Civil War relied heavily on fieldwork by detailing the roles of spies, their strategies, and the risks involved. This information highlights the human element's significance in intelligence-gathering despite technological advancements. Therefore, the best answer choice is C: by including more detailed information about who did fieldwork for the Union and how it was done.
;