General Grant turned his attention to trying to destroy the railroads, and made several attempts with much hard fighting to do so. But this, having been anticipated by General Lee, he had given to A. P. Hill the defense and the protection of the railroads, which was his source of supplies. They were ably protected by General Hill, and Grant's attacking parties in every instance were repulsed, and these plans were at length abandoned by him for the present. The two armies lay facing each other before Petersburg the entire summer and fall, with several small engagements during the summer and a few very severe ones. A severe cavalry engagement was fought at Trevilian Station, north of Richmond, on June 11th, between the Confederates, commanded by Generals Hampton and Fitzhugh Lee, and the Federals, commanded by General Sheridan. During the latter days of July the Federals were engaged in digging a mammoth tunnel, beginning in the rear of their entrenchments and to extend under the Confederate fortifications before Petersburg, at the completion of which they expected to fill the same with large quantities of gunpowder which was to be exploded and was expected to blow up the Confederate fortifications. Of all the schemes employed by either army this was the greatest, and one in which Grant had great faith, and the progress of which was watched with great anxiety. The Confederates were apprised of this undertaking, and had made ready by placing several batteries within their lines so that the fire from the same would sweep the opening which would be made by the blowing up of the "crater." At a few minutes past five on the morning of July 30th this mine was exploded, which was a sight to behold. The Federal troops who were in waiting to march through the opening were somewhat delayed from the shock and horror of the explosion, but at length marched in the opening in great numbers, and by this time the Confederate batteries were brought into action, which so horribly swept their ranks, and they were charged by General Mahone with several divisions of Georgia troops, and the Federal loss became so great, and their ranks in so much confusion, that they were ordered to retire within their entrenchments, thus bringing to a dismal failure the capture of Petersburg by this plan. [Illustration: BATTLE OF SPOTTSYLVANIA COURT-HOUSE] During the last days of August Grant renewed his plan to destroy the Weldon railroad. This task was given to General Warren, with a large force who, after fighting several hard battles with the dashing Mahone, whose numbers were greatly inferior to that of Warren, and from his reputation for strategy it is thought that he was very worthy to wear the mantle of "Stonewall" Jackson, the Federals succeeded in destroying this railroad in several places.