In its outcome, this enterprise which had been planned for the destruction of Lee and his army, resulted rather in their strengthening. Having recaptured the crater they promptly threw up a line of works along that side of it which lay nearest to their enemy, thus in fact, shortening the distance between the two lines, without in any way weakening their position.
An unfortunate circumstance connected with this affair was the fact that General Burnside, who had general command in that part of the field, made a desperate endeavor--which came a few minutes too late--to force the Confederate second line by an advance of the negro troops under his command. These pushed themselves as far forward up the hill as they could go and were there hurled back and driven into the great pit. In the event many of them were captured. The Confederates refused to recognize these black men as soldiers or to treat them as prisoners of war. It was a time, indeed, when the Southern soldiers were in a state of peculiar exasperation and revengefulness against negroes in arms. During a recent raid certain negro troops had committed unforgiveable outrages upon women, and in consequence the mood of mind of the Army of Northern Virginia was such that a negro soldier in arms had better have fallen into hell than into their hands. General Lee and his subordinates did what they could to compel a merciful treatment for the negro troops who were captured in the crater. It was all to no purpose. Every effort made to send these men to the rear as prisoners under charge of details ended in a report from the commander of the detail that the negroes had "escaped." Their escape was of such kind that burial parties had to be sent into the covered ways leading to Petersburg to clear them of the negro corpses there.
General Grant has said of this mine enterprise: "The effort was a stupendous failure. It cost us about 4,000 men, mostly however, captured; and all due to inefficiency on the part of the corps commander (Burnside) and the incompetency of the division commander (Ledlie) who were sent to lead the assault."
It will be remembered that General Grant set out upon his Virginia campaign of 1864 with the definite and avowed purpose of crushing and destroying Lee in the field. The completeness of his failure to accomplish this purpose was made manifest in July, when Lee, confronting the consolidated armies of the Potomac and the James, nevertheless felt himself strong enough to detach from his own force a vigorous body of troops under Early, with instructions to sweep Hunter out of the Valley of Virginia and undertake a third invasion of Maryland, so conducted as to threaten Baltimore and Washington.