The major result of the opening 4 days of combat, however, was the failure of the Federal forces to break the Confederate defense line. First Beauregard, and then Lee, had held against heavy odds. They had been pushed back closer to their base—but they had held. Possibly if Smith had advanced his XVIII Corps farther into the defenses on the opening night, Petersburg would have fallen on June 15 or 16. But that had not been done, and the campaign was to run nearly 10 more months. The lines of battle before Petersburg were clearly drawn. Between 47,000 and 51,000 men defended it against 111,000 to 113,000 besiegers. The defenses of Richmond now stretched from White Oak Swamp, east of that city, south to the Jerusalem Plank Road, 26 miles away. The fate of the Army of Northern Virginia—of the Confederate capital itself—would depend upon the outcome of the drive against Petersburg. _First Union Attempt on the Weldon Railroad_ The Union Army, having failed in its initial attack on Petersburg, was now committed to doing something further to effect its capture. The period from June 19 to July 9 was spent in three types of activity. First, elements of the army were set to work consolidating the positions captured in the 4-day battle and constructing the devices needed for siege operations. A second type of effort consisted of jabbing thrusts at the important supply routes into Petersburg. The last was a reconnoitering of the Confederate defenses to determine a plan which would result in the fall of the city. A threatening movement toward the Weldon Railroad was soon made by the Northern troops. Three days after the failure to capture the city a small force began to push to the southwest of Grant’s flank on the Jerusalem Plank Road. The following day, June 22, Confederate divisions led by Generals Cadmus M. Wilcox and William Mahone advanced from the defense line south of Petersburg and forced the Union troops to a temporary halt. The next morning saw the resumption of the advance toward the Weldon Railroad. A small cavalry force was successful in reaching the tracks on the 23d, and it promptly started the work of destruction which was its mission. Alarmed by the threat to this important supply line, the Confederates launched a sharp attack which forced the withdrawal of the Union forces from the vicinity of the railroad. However, the Union lines confronting Petersburg had been extended across the Jerusalem Plank Road, thus cutting off its use to the city.