The Iron Brigade was heavily engaged, at the Battle of South Mountain and had just been taken command of by Colonel Walter Phelps Jr of the 22nd New York Volunteer Infantry Regiment the day of South Mountain. The Iron Brigade received orders to make their advance up the mountain around 4 pm to support General Patrick's brigade in assaulting the confederate positions atop the hill. They were sent in as skirmishers to assist Colonel Patrick's men and then were posted behind a fence awaiting the command to move forward.