Two weeks of Union delay before the Battle of Fredericksburg gave the Confederates time to bring up large cannons rarely seen on other battlefields in Virginia. Sturdy gun emplacements on Howison Hill protected a huge siege gun capable of firing a 30-pound shell nearly two miles. Ten men operated the cannon, and a gun like this typically fired a round every five minutes. As they awaited battle, Confederate cannoneers cut down trees and carefully calculated the range to likely areas of Union attack. When the fighting started on December 13, 1862, the Confederate guns on Howison Hill fired rhythmically on Union columns in front of Marye's Heights, and the crossfire from Howison Hill added horror to an already impossible Union task.