Despite these 11th-hour changes, a plan of battle had been evolved. During the night of July 29-30, the bulk of the IX Corps was assembled in the ravine behind the mine entrance and in the two approach trenches leading to the picket line. Troops from other Union corps were marshalled as reinforcements. Artillerymen, manning 110 guns and 54 mortars, were alerted to begin shelling the Confederate line. To assist the attack, Grant sent a cavalry and infantry force north of the James to threaten the Richmond defenses and destroy whatever they could of the Virginia Central Railroad. The object was to draw as many of Lee’s soldiers away from Petersburg as possible. And it worked. When the assault came, only 18,000 Confederates were left to guard the city. At 3:15 a.m., July 30, Pleasants lit the powder fuse and mounted the parapet to see the results of his regiment’s work. The explosion was expected at 3:30 a.m. Time passed slowly and the men, huddled behind the lines, grew more apprehensive. By 4:15 there could be no doubt that something had gone wrong. Two volunteers from the 48th Regiment (Lt. Jacob Douty and Sgt. Harry Reese) crawled into the tunnel and found that the fuse had burned out at a splice. They relighted it and scrambled to safety. Finally, at 4:40 a.m., the earth trembled, and with one great roar, men, equipment, and debris were hurled high into the air. At least 278 Confederate troops were killed or wounded in the tremendous blast, and two of the four guns in the battery were destroyed beyond repair. The crater torn by the powder was at least 170 feet long, 60 to 80 feet wide, and 30 feet deep. The awesome spectacle of the mine explosion caused a delay in the Union charge following the explosion. Removal of obstructions between the lines caused further delay. Soon, however, an advance was made to the crater, where many of the attacking force paused to seek shelter on its steep slopes or to look at the havoc caused by the mine. The hard-pressed Confederates rallied quickly and soon were pouring shells and minié balls into their opponents. Union reinforcements poured into the breach; but, instead of going forward, they either joined their comrades in the crater or branched out to the immediate right and left along the lines. By 8:30 that morning a large part of the IX Corps had been poured into the captured enemy salient. More than 15,000 troops now milled in and about the crater. By prompt action and determined effort the Confederates had prevented a breakthrough. The attention of three batteries was soon directed on the bluecoats at the crater. Artillery hammered with shot and shell the huddled groups of increasingly demoralized men. In addition, mortars brought to within 50 yards of the crater dropped shells on the soldiers with deadly effect.