What impact did slavery have on the war effort in the South?

Slavery impacted the war effort in the South by decreasing the efficiency of the military in the war.

Explanation:

The military forces in the South had to perform two distinct duties during the course of war. One of which was to fight with the military forces of the North and the other was to keep the slaves under control. This directly affected the efficiency of the military of the South and eventually resulted in their loss.