The great campaign between Confederate General Robert E. Lee's Army of Northern Virginia and Ulysses S. Grant's Army of the Potomac ground to a halt in mid-June. Having battered each other for a month and a half, the armies came to a standstill at Petersburg, just south of Richmond. Here, they settled into trenches for a long siege of the Confederate rail center.
The men of the 48th Pennsylvania sought to break the stalemate with an ambitious project. The brainchild of Lieutenant Colonel Henry Pleasants, the plan called for the men of his regiment–mostly miners from Pennsylvania's anthracite coal region–to construct a tunnel to the Confederate line, fill it with powder, and blow a gap in the fortifications.
On June 24, the plan received the approval of the regiment's corps commander, Ambrose Burnside, and the digging commenced the following day. Burnside's superiors, Generals Grant and George Meade, expressed little enthusiasm for the project but allowed it to proceed. For five weeks the miners dug the 500-foot long shaft, completing about 40 feet per day.
On July 30, a huge cache of gunpowder was ignited. The plan worked, and a huge gap was blown in the Rebel line. But poor planning by Union officers squandered the opportunity, and the Confederates closed the gap before the Federals could exploit the opening. The Battle of the Crater, as it became known, was an unusual event in an otherwise uneventful summer along the Petersburg line.