The Confederate picket line was overwhelmed quickly by the Union attackers. Despite the heavy fire from the main Confederate defenses and batteries, much of the initial artillery fire from the defenders was too high to hit the Union men, but the Confederate gunners soon adjusted their range. The Vermont Brigade began to falter under the more well-directed musket and artillery fire. Although the account of a soldier from the 4th Vermont Infantry Regiment stated that as many as half broke for the rear and others stopped at the pickets' rifle pits, Captain Merritt Barber of the Vermont Brigade said most mustered their courage and plunged ahead. The Confederate main line was reached through openings cut away by the pioneers and existing openings left by Confederates to provide access to the front. Many Union soldiers reached the obstructions before the pioneers and tore them away with bare hands or found small openings to pass through. Most of the Union casualties were suffered while the soldiers crossed the ground between the pickets' rifle pits and the obstructions.