In June 1864, Grant attempted to seize the Confederate rail hub of Petersburg, Virginia. General P.G.T. Beauregard responded by rushing troops to Petersburg to protect the vital supply lines. A stalemate developed between the entrenched armies. Union commander General Ambrose Burnside advanced the idea of allowing the 48th Pennsylvania--a regiment from the mining town of Pottsville--to tunnel under Confederate entrenchments and place explosives...