put Porter in grave jeopardy, without any last-minute reinforcements and the cover of darkness. He quotes Edward Porter Alexander, prominent Confederate artillery officer and postwar historian: "Had Jackson attacked when he first arrived, or during A.P. Hill's attack, we would have had an easy victory—comparatively, & would have captured most of Porter's command." Although McClellan had already planned to shift his supply base to the James River, his defeat unnerved him and he precipitously decided to abandon his advance on Richmond and begin the retreat of his entire army to the James. Gaines' Mill and the Union retreat across the Chickahominy was a psychological victory for the Confederacy, signaling that Richmond was out of danger. Battlefield preservation The only preserved portion of the Gaines' Mill battlefield for nearly 150 years was a 60-acre section of the battlefield under National Park Service control around the Watt House. This tract is only a small fraction of the more than 2,000 acres that comprises the battlefield. In 2011, two preservation efforts were completed by the Richmond Battlefields Association and the American Battlefield Trust, the first preservation successes at Gaines' Mill since before World War II. This new 285-acre "Longstreet Attack" tract greatly expanded the amount of preserved land at Gaines' Mill. The American Battlefield Trust and its partners have preserved a total of of the battlefield through land acquisitions or easements. See also Troop engagements of the American Civil War, 1862 List of costliest American Civil War land battles Richmond in the Civil War Virginia in the American Civil War List of American Civil War battles List of Virginia Civil War units Notes References Burton, Brian K. Extraordinary Circumstances: The Seven Days Battles. Bloomington: Indiana University Press, 2001. . Editors of Time-Life Books. Lee Takes Command: From Seven Days to Second Bull Run. Alexandria, VA: Time-Life Books, 1984. . Eicher, David J. The Longest Night: A Military History of the Civil War. New York: Simon & Schuster, 2001. . Kennedy, Frances H., ed. The Civil War Battlefield Guide. 2nd ed. Boston: Houghton Mifflin Co., 1998. . Salmon, John S. The Official Virginia Civil War Battlefield Guide. Mechanicsburg, PA: Stackpole Books, 2001. . Sears, Stephen W. To the Gates of Richmond: The Peninsula Campaign. New York: Ticknor and Fields, 1992. . Welcher, Frank J. The Union Army, 1861–1865 Organization and Operations. Vol. 1, The Eastern Theater. Bloomington: Indiana University Press, 1989. . National Park