Digging was finally completed on July 23. Four days later the task of charging the mine with black powder was accomplished. Three hundred and twenty kegs of powder weighing, on the average, 25 pounds each were arranged in the two lateral galleries in eight magazines. The total charge was 4 tons, or 8,000 pounds. The powder was sandbagged to direct the force of the explosion upward and two fuses were spliced together to form a 98-foot line. Meanwhile, preparations for the attack which was to follow the explosion of the mine had been carried out. Burnside was convinced of the necessity for a large-scale attack by the entire IX Corps. His request was acceded to by Meade and Grant with but one important exception. It had been Burnside’s hope that a fresh and numerically strong (about 4,300) Negro division should lead the charge after the explosion. Meade opposed this on the grounds that if the attack failed the Union commanders could be accused of wanting to get rid of the only Negro troops then with the Army of the Potomac. Burnside was not informed of this decision until the day before the battle, July 29, and he was forced to change his plans at the last moment. Three white divisions were to make the initial charge along with the colored troops. Burnside had the commanding generals of these three divisions draw straws to see which would lead. Gen. James F. Ledlie of the 1st Division won the draw. Despite these eleventh-hour changes, a plan of battle had been evolved. During the night of July 29-30 the bulk of the IX Corps had assembled in the ravine behind the mine entrance. Troops from other Union corps were sent to act as reinforcements. A total of 110 guns and 54 mortars was alerted to begin their shelling of the Confederate line. A Union demonstration before Richmond had forced Lee to withdraw troops from Petersburg. Only about 18,000 soldiers were left to guard the city. [Illustration: _A contemporary sketch by Waud showing the Union charge to the Crater._ From Battles and Leaders of the Civil War.] [Illustration: _The Crater as it appeared in 1865. The Union soldier seated at the end of the tunnel gives an idea of the size of the Crater._ Courtesy, National Archives.]