In July, 1862 the first Negro troops of the Civil War were organized by General David Hunter. Known as the 1st South Carolina Regiment, they were later designated the 33rd Regiment United States Colored Troops. Some 186,000 Negro soldiers served in the Union Army, 4,300 of whom became battle casualties. At the battle of Fredericksburg in 1862, the line of Confederate trenches extended a distance of seven miles. The troop density in these defensive works was 11,000 per mile. Over 900 guns and mortars bristled from the 68 forts defending the Nation's Capital during the war. The fortifications, constructed by the Engineer Corps during the early part of the war, circled the city on a 37-mile perimeter. During Sherman's campaign from Chattanooga to Atlanta, the Union Army of the Tennessee, in a period of four months, constructed over 300 miles of rifle pits, fired 149,670 artillery rounds and 22,137,132 rounds of small-arms ammunition. To fire a Civil War musket, eleven separate motions had to be made. The regulation in the 1860's specified that a soldier should fire three aimed shots per minute, allowing 20 seconds per shot and less than two seconds per motion. At the battle of Stone's River, Tennessee, in January, 1863, the Federal infantry in three days exhausted over 2,000,000 rounds of ammunition, and the artillery fired 20,307 rounds. The total weight of the projectiles was in excess of 375,000 pounds. At the Battle of First Bull Run or Manassas, it has been estimated that between 8,000 and 10,000 bullets were fired for every man killed and wounded. The campaign against Petersburg, the longest sustained operation of the war, began in the summer of 1864 and lasted for 10 months, until the spring of '65. The fighting covered an area of more than 170 square miles, with 35 miles of trenches and fortifications stretching from Richmond to the southwest of Petersburg. During September, 1864, nearly 175 field and siege guns poured forth a daily average of 7.8 tons of iron on the Confederate works. The greatest cavalry battle in the history of the western hemisphere was fought at Brandy Station, Virginia, on June 9, 1863. Nearly 20,000 cavalrymen were engaged for more than 12 hours. At the height of the battle, along Fleetwood Hill, charges and countercharges were made continuously for almost three hours. The greatest regimental loss of the entire war was borne by the 1st Maine Heavy Artillery. The unit saw no action until 1864, but in the short span of less than one year, over half of its 2,202 men engaged in battle were hit. In the assault on Petersburg in June, 1864, the regiment lost 604 men killed and wounded in less than 20 minutes. The largest regimental loss in a single battle was suffered by the 26th North Carolina Infantry at Gettysburg. The regiment went into battle with a little over 800 men, and by the end of the third day, 708 were dead, wounded, or missing. In one company of 84, every officer and man was hit.