losses. One of the leading regiments was the 1st Maine Heavy Artillery Regiment, 900 men that had been converted from essentially garrison duty manning artillery to be infantrymen at the start of the Overland Campaign. The regiment quickly lost 632 men in the assault, the heaviest single-battle loss of any regiment during the entire war. Aftermath Having achieved almost no gains from four days of assaults, Meade ordered his army to dig in. Union casualties were 11,386 (1,688 killed, 8,513 wounded, 1,185 missing or captured), Confederate 4,000 (200 killed, 2,900 wounded, 900 missing or captured). Grant's opportunity to take Petersburg easily had been lost, but Lee, who arrived at Petersburg around noon on June 18, was unable to prevent the Union army from laying siege to the city. The siege would last until April 1865. See also Troop engagements of the American Civil War, 1864 Overland Campaign Battle of Cold Harbor Siege of Petersburg List of costliest American Civil War land battles Notes References Bonekemper, Edward H., III. A Victor, Not a Butcher: Ulysses S. Grant's Overlooked Military Genius. Washington, DC: Regnery, 2004. . Chick, Sean Michael. The Battle of Petersburg, June 15–18, 1864. Lincoln, NE: Potomac Books, 2015. Davis, William C., and the Editors of Time-Life Books. Death in the Trenches: Grant at Petersburg. Alexandria, VA: Time-Life Books, 1986. . Eicher, David J. The Longest Night: A Military History of the Civil War. New York: Simon & Schuster, 2001. . Esposito, Vincent J. West Point Atlas of American Wars. New York: Frederick A. Praeger, 1959. . The collection of maps (without explanatory text) is available online at the West Point website. Fuller, Major General J. F. C. Grant and Lee, A Study in Personality and Generalship. Bloomington: Indiana University Press, 1957. . Howe, Thomas. Petersburg Campaign: Wasted Valor June 15–18, 1864. Lychburg, VA: H. E. Howard, 1988. 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. . Trudeau, Noah Andre. The Last Citadel: Petersburg, Virginia, June 1864 – April 1865. Baton Rouge: Louisiana State University Press, 1991. . National Park Service battle description CWSAC Report Update Memoirs and primary sources Grant, Ulysses S. Personal Memoirs of U. S. Grant. 2 vols. Charles L. Webster & Company, 1885–86. . Longstreet, James. From Manassas to Appomattox: Memoirs of