In the meanwhile, he was attached to Brigadier general Nathaniel Lyon's Union Army of the West. Sigel and his soldiers helped put down a riot the St. Louis area. The incident was known as the Camp Jackson Affair. He led a Flanking maneuver at Battle of Wilson's Creek, surprising and attacking the Confederate forces from their rear while Lyon attacked them from the front. On March 8, 1862, at the Battle of Pea Ridge, Sigel commanded two division (military)s in the victory against Major General Earl Van Dorn (CSA).