The 13-inch mortar called "Dictator," a seige weapon, mounted on a railroad flatcar during the Siege of Petersburg. The Union army attacked Petersburg, Virginia, in series of battles from June 9, 1864 to March 25, 1865, with the intention of cutting off Petersburg as a supply source to the Confederate army during the American Civil War. In the foreground, the figure on the right is Brig. Gen. Henry J. Hunt, chief of artillery of the Army of the Potomac.