On May 31-June 1, 1862 the Battle of Seven Pines or Fair Oaks took place. The left wing of the Union army under McClellan was attacked by Confederate General Joseph E. Johnston at Fair Oaks Station and Seven Pines, located just east of Richmond. The Confederates won at Seven Pines but were driven back at Fair Oaks. The Battle of Seven Pines was considered indecisive. General Johnston was wounded seriously in this battle, and, at this time, General Robert E. Lee was put in command of the Army of Northern Virginia. On June 8-9, Jackson was slowly retreating up the Shenandoah Valley when he decided to prevent two Union generals, John C. Fremont and James Shields, from combining forces by checking or holding back Fremont and then attacking Shields. He sent part of his troops under General Richard S. Ewell to attack the forces under Fremont at Cross Keys in Rockingham County. General Ewell defeated the forces of Fremont very badly and kept Fremont's help completely away from Shields. Jackson then led his remaining forces north of Port Republic and encountered Shields there. Bitter fighting followed. Shields was eventually defeated and driven down the Shenandoah Valley. This was the final engagement of the so-called Valley campaign. Jackson had proven himself a great military man who had fought on both sides of the Shenandoah Valley and who had marched approximately 700 miles in seven weeks in almost continuous fighting with one or more of the Federal fighting forces. This campaign included five major engagements: Kernstown, McDowell, Front Royal, Winchester and Port Republic. Jackson suffered defeat only at Kernstown by the Union General James Shields. Jackson then proceeded toward Richmond to prevent General McClellan from entering there. On June 11, General Lee dispatched General James Ewell Brown ("J. E. B.") Stuart with 1200 cavalry and infantrymen from Richmond to obtain information behind the lines of the enemy concerning the specific position of McClellan. In three days, Stuart and his contingent had courageously ridden completely around the army of McClellan, acquiring much valuable information for General Lee. Only one of Stuart's men was killed during the assignment. Based upon the information furnished by General "J. E. B." Stuart, General Lee decided to advance his army on June 26. The Union forces under General Fitz-John Porter had outposts near Richmond just north of the Chickahominy River in the town of Mechanicsville. Confederate General Ambrose P. Hill successfully occupied Mechanicsville and then continued to attack General Fitz-John Porter's troops along Beaver Dam Creek where he severely defeated them.