The Union Ninth Corps moved up two covered ways, wide and deep trenches, to reach the Crater, with one on the left atop the bluff along the wood line and the other to the right. On the morning of the explosion, lead Union troops lay behind the picket line on the bluff above. A Union soldier remembered, "The night was not very dark, a waning moon hung phantom-like in the north-east, over our pine woods. The column was closely massed in regimental lines of battle, but without noise, fearing to alarm the enemy." The 3rd Division of the Ninth Corps went through the covered way on the left into the battle and into a "storm of every conceivable missile," then swung south of the Crater to stem Confederate counterattacks. Next came the all-black 4th Division, which had been trained to lead the assault but was switched to the rear before the explosion. As they came up, their commander, Colonel Henry Thomas, realized, "The crater was already to full; that I could easily see," and led his men north of it under intense Confederate fire. Division commanders of the Union 9th Corps were General James Ledlie of the 1st Division, General Robert Porter of the 2nd Division, General Orlando Willcox of the 3rd Division, and General Edward Ferrero of the 4th Division.