At several places east of the city the opposing lines were extremely close together. One of these locations was in front of Elliott's Salient, a Confederate strong point near Cemetery Hill and old Blandford Church. Here the Confederate position and the Union picket line were less than 400 feet apart. Because of the proximity of the Union line, Elliott's Salient was well fortified. Behind earthen embankments was a battery of four guns, and two veteran South Carolina infantry regiments were stationed on either side. Behind these were other defensive works; before them the ground sloped gently downward toward the Union advance line.
This forward Union line was built on the crest of a ravine which had been crossed on June 18. Through this ravine, and between the sentry line and the main line, lay the roadbed of the Norfolk and Petersburg Railroad. The front in this sector was manned by Gen. Ambrose E. Burnside's IX Corps. Among the many units which composed this corps was the 48th Regiment, Pennsylvania Veteran Volunteer Infantry. A large proportion of this regiment had been coal miners, and it seemed to have occurred to one or more of them that Elliott's Salient would provide an excellent place to use their civilian occupation. Lt. Col. Henry Pleasants, the commanding officer of the 48th and a mining engineer by profession, overheard one of the enlisted men mutter, "We could blow that damned fort out of existence if we could run a mine shaft under it." From this and similar remarks came the germ of the idea for the Union mine. This is what the 48th Regiment proposed to do: dig a long gallery from the bottom of the ravine behind their picket line to a point beneath the Confederate battery at Elliott's Salient, blow up the position by means of powder placed in the end of the tunnel, and, finally, send a strong body of troops through the gap created in the enemy's line by the explosion. They saw as the reward for their effort the capitulation of Petersburg and, perhaps, the end of the war.