On July 30, 1863, President Abraham Lincoln issued the "eye-for-eye" order to shoot a rebel prisoner for every black prisoner shot. From the article:
"On this date in 1863, President Abraham Lincoln issued what was called an "eye-for-eye" order, warning the Confederacy that Union soldiers would shoot a rebel prisoner for every black prisoner shot. It also would condemn a rebel prisoner to a life of hard labor for every Black prisoner sold into slavery.
The order had a slight "restraining" influence on the Confederate government's voiced policy, but individual commanders and soldiers continued to murder captured black soldiers.
Although this act appeared to be motivated by feelings of compassion toward the slaves, it was intended primarily as another way to intimidate the Confederacy."