To send forward such men against the fortifications of Petersburg, manned by Lee's veteran troops, was to court defeat, and he therefore began to throw up works for a regular siege.
Fighting went on incessantly between the outposts, but only one great attempt was made during the early months of the siege to capture the Confederate position.

The miners drove a gallery under the works, and then drove other galleries right and left under them.

These were charged with eight thousand pounds of powder.

When all was ready, masses of troops were brought up to take advantage of the confusion which would be caused by the explosion, and a division of black troops were to lead the assault.

At a quarter to five in the morning of the 30th of July the great mine was exploded, blowing two guns, a battery, and its defenders into the air, and forming a huge pit two hundred feet long and sixty feet wide.