Well, some red stuff says that "need more than 20 letters", so that's why I'm typing this up.
T-R-U-E
It's true! :)
While you didn't really provide the "following" as the comment above me states, in general, the advantage of secondary sources of primary ones is that they perhaps provide a more objective or even just a broader view on a certain topic. While a primary source of the American civil war would be a letter written by a soldier, a secondary source would be a book that describes more letters taken together and discusses possible information regarding them.
Answer:
During the battle, McClellan kept four divisions of soldiers in reserve and refused to use them to attack Lee's devastated army. McClellan was convinced that Lee was massing reserves for a counterattack.
Explanation:
