Meanwhile, Price had been reinforced by a small Confederate army under the command of Benjamin McCulloch. On August 10, Lyon decided to attack Price and McCulloch's combined forces while the Confederate were encamped along the banks of Wilson's Creek. Lyon split his outnumbered forces into wings commanded by himself and Col. Franz Sigel in order to attack the Confederate camp from both the front and the rear. Sigel's force was soon driven from the field, allowing Price and McCulloch to combine their forces against Lyon's column, which had taken position on Bloody Hill. Lyon was killed, and the Union forces retreated from the field. It was the first major military engagement in the American Civil War to take place west of the Mississippi river.