On a hot and humid summer day, Confederate forces faced a steep challenge in trying to retake the high ground, where more than 4,000 Union soldiers and 10 artillery pieces stood ready to repel them. As Southern infantry launched repeated charges up the hill, Captain Henry Guibor's four-gun battery of the Sixth Division, Missouri State Guard, was assigned to this position to support the attack. Operating within musket range of Union cavalry and infantry, the battery fired shell and canister into the Federal line during the Confederates' third and final charge. That assault involved about 6,000 soldiers drawn up in a battle line 1,000 yards long, and Union commander Maj. Samuel Sturgis called it the fiercest and bloodiest engagement of the day.