My husband’s g-grandfather was at the Siege of Petersburg and we’ve visited the battlefield twice; some of the mine tunnels and the crater itself are still there.
The Union officer in command at the Battle of the Crater was Ambrose Burnside, not the sharpest knife in the drawer. He was responsible for the fiasco of Marye’s Heights at the Battle of Fredericksburg, which Wikipedia describes as “one of the most one-sided battles of the war, with Union casualties more than twice as heavy as those suffered by the Confederates.”
Our kids were just 8 or 9 when we first went to Petersburg, and even they realized that riding into the crater was crazy. From what I remember hearing at the battlefield, it was dark, 4:40 AM, and then the cavalry was carried away with fighting madness. They’d been idle during the siege for weeks, and when finally something was happening, they reacted impulsively.
The History and Culture section of the Petersburg National Battlefield page says “Throughout the 9.5 month siege of Petersburg, 70,000 soldiers became casualties in an event considered to be a precursor to World War I.”
Petersburg National Battlefield (U.S. National Park Service) (nps.gov)