Lieutenant Whitside served with his company in the 6th Cavalry during the Peninsular Campaign of 1862 where he participated in the following battles: Williamsburg – May 5, Slatersville – May 7, New Bridge – May 20, Ellison's Mills – May 23, Hanover Court House – 27 to May 29, Black Creek – June 26, and Malvern Hill – August 5.