He never stopped until he had flanked Lee's army by a wide swing, made his way to the rear and joined the Confederacy. Grant had now changed his plan of campaign. He determined to capture Petersburg by a _coup_ and cut the communication of Lee and Richmond with the South. The _coup_ failed. The ragged remnants of Lee's army which had been left there to defend it, held the trenches until reinforcements arrived. He determined to take it by a resistless concerted assault. On the 16th he threw three of his army corps on Beauregard's thin lines before Petersburg, capturing four redoubts. At daylight, on the 17th, he again hurled his men on Beauregard and drove his men out of his first line of defense. All day the defenders held their second line, though Grant's crack divisions poured out their blood like water. As night fell the dead were once more piled high on the Federal front and the Confederate dead filled the trenches. As the third day dawned the fierce, assault was renewed, but Lee had brought up Anderson's Corps with Kershaw and Field's division and the blue waves broke against the impregnable grey ranks and rolled back, leaving the dead in dark heaps. As the shadows of night fell, Grant withdrew his shattered lines to their trenches. _He had lost ten thousand five hundred more men and had failed._ He began to burrow his fortifications into the earth around Petersburg and try by siege what had been found impossible by assault. Further and further crept his blue lines with pick and axe and spade and shovel, digging, burrowing, piling their dirt and timbers. Before each blue rampart silently grew one in grey until the two siege lines stretched for thirty-seven miles in bristling, flaming semicircle covering both Richmond and Petersburg. Again Grant planned a _coup_. He chose the role of the fox this time instead of the lion. He selected the key of Lee's long lines of defense and set a regiment of Pennsylvania miners to work digging a tunnel under the Confederate fort known as "Elliot's Salient," which stood but two hundred yards in front of Burnside's corps. The tunnel was finished, the mine ready, the fuses set, and eight thousand pounds of powder planted in the earth beneath the unsuspecting Confederates. Hancock's division with Sheridan's cavalry were sent to make a demonstration against Richmond and draw Lee's main army to its defense. The ruse was partly successful. There were but eighteen thousand behind the defenses of Petersburg on the dark night when Grant massed fifty thousand picked men before the doomed fort. The pioneers with their axes cleared the abatis and opened the way for the charging hosts. Heavy guns and mortars were planted to sweep the open space beyond the Salient and beat back any attempted counter charge.