There were no Union attacks directly against Richmond in 1863. The second great movement upon the Confederate Capital began in June, 1864, when Grant came down through the Wilderness, as already described, and attacked the Confederates at Cold Harbor. Lee was entrenched there in almost the same defensive position occupied by McClellan's rear when protecting his retreat across the Chickahominy two years before. Grant made little impression, but in a brief and bloody battle lost fifteen thousand men. He then turned aside from this almost impregnable position to the northeast of Richmond, went south to the James River, and, crossing over, started a new attack from a different quarter. This removed the seat of war to the south of Richmond, and in September, 1864, General Butler's Unionist troops from Bermuda Hundred captured Fort Harrison, a strong work on the northeast side of the James, opposite Drewry's Bluff, and not far from Malvern Hill. The campaign then became one of stubborn persistence. Throughout the autumn and winter Grant gradually spread his lines westward around Petersburg, so that the later movements were more a siege of that city than of Richmond. City Point, at the mouth of the Appomattox, flowing out from Petersburg to the James, became his base of supplies. As the Union lines were extended steadily westward, one railway after another, leading from the far South up to Petersburg and Richmond, was cut off, and Lee was ultimately starved out, forcing the abandonment of Petersburg in the early spring of 1865, and the evacuation of Richmond on April 3d, with the retreat of Lee westward, and the final surrender at Appomattox six days later, causing the downfall of the Confederacy, and ending the war.