By August 9th, Union Brigadier General Nathaniel Lyon had decided to attack the Confederates encamped around Wilson's Creek. Although opposed by most of his officers, Lyon had decided to follow Sigel's recommendation to split his forces. Sigel would move his brigade around to the east and attack the Confederates from the south as reported by Lyon's aide, Major John M. Schofield.
"During the forenoon of [the 9th Of August], General Lyon and Colonel Sigel held a consultation, the result of which was the plan of attack upon the enemy's position at Wilson's Creek.... General Lyon informed me of his determination to make the attack the next morning and gave me the general features of the plan but owing to the press of time did not go into much detail. Colonel Sigel was to move with his brigade ... to the left [east] of the main Casaville Road leading to the right [south] of the enemy position, while General Lyon with the remainder of the force ... was to move down the road toward Little York ... and attack his left [north] flank. Colonel Sigel was to make his attack as soon as he heard that of General Lyon."