Battle of the Crater

'At that point, everything deteriorated rapidly for the Union attackers. Unit after unit, most of whom were U. S. Colored Troops, charged into and around the crater, where most of them milled in confusion in the bottom of the crater. Grant considered this failed assault as "the saddest affair I have witnessed in this war."[4]" - https://en.wikipedia.org/wiki/Battle_of_the_Crater#Aftermath