Has it happened an all black batallion was to lead the assault. But instead of going around the massive crater they first went in and got trapped in the cauldron when confederates recovered and flooded the crater with shot and mortar. It turned into a debacle and the confederates gave the black soldiers no quarter.
Makes me think of the scene in the Russian movie “Brest Fortress” where the Germans dropped a two-ton bomb on the fortress, that sunk into the ground before detonating.
The same thing happened in Vicksburg on June 25, 1863, except for it was white troops who rushed into the crater.
http://www.nps.gov/vick/historyculture/tour-stop-3-third-la-redan.htm