The Political Subtext of Gingrich's New Novel
In his new Civil War retelling, Gingrich focuses on a regiment of black Union soldiers -- but downplays the racism they faced, a historian says

More conspicuous in its absence, however, is any description of how Confederates felt at having to fight armed black men for the first time just outside of a large civilian population, as well as the accounts of their execution following the battle. The closest the authors come to acknowledging this is in a Confederate officer's conversation with Garland White following the battle, in which he shares that "after our boys retook the lip of the crater, the cry went up to kill all the colored." He is quick to point, however, his own position on slavery: "My family refused to own them. We hired free blacks to work the fields of our farm. So yes, I tried to stop it, so did most of the officers."
Even a cursory glance at the available evidence points to the unlikelihood of such a scene.
...
The presence of black soldiers at the Crater confirmed for slaveowners and non-slaveowners in the ranks just what was at stake in the event of Confederate defeat. The massacre of black soldiers constituted a calculated response when viewed alongside the actions of white southerners throughout the antebellum period to slave rebellions both real and imagined.
The authors go out of their way to remove any sense of how Confederates responded to the presence of black soldiers, even going so far as to construct a fictional meeting in which Robert E. Lee encourages General William Mahone to take steps to ensure complete victory and prevent the mistreatment of captured black soldiers: "I want the full honor of war observed. Those who surrender are to be treated as proper prisoners, with respect, their wounded tended to, their officers shown the respect due their rank."
Suffice it to say that there is no evidence of such a meeting nor is there any evidence that Lee attempted to prevent the execution of black soldiers following the battle. The absence of any written correspondence from Lee on this matter suggests that he, in all likelihood, condoned it.