Late that afternoon, more Union soldiers, led by Major General Ambrose Burnside, came into the fight. They captured a stone bridge over Antietam Creek and moved towards the Confederate troops' right side. But as Burnside's soldiers attacked, more Confederate soldiers arrived. Confederate Major General A.P. Hill had led his division of soldiers from Harpers Ferry to Antietam. Once Hill's division arrived, they were able to counterattack (fight back against Burnside's soldiers). This was a surprise to the Union troops, and the surprise worked well. The Confederate troops drove Burnside's soldiers back and ended the battle. Even though he had more soldiers, McClellan was not able to destroy Lee's army. Lee was able to shift his troops to meet each of McClellan's attacks. McClellan also did not call up his many reserve forces (soldiers on standby) which could have helped build on the Union's successes.