After defeating Major General John C. Frémont's force in the Battle of McDowell, Jackson turned against the forces of Major General Nathaniel Banks. Banks had most of his force at Strasburg, Virginia, with smaller detachments at Winchester and Front Royal. Jackson attacked the position at Front Royal on May 23, surprising the Union defenders, who were led by Colonel John Reese Kenly. Kenly's men made a stand on Richardson's Hill and used artillery fire to hold off the Confederates, before their line of escape over the South Fork and North Fork of the Shenandoah River was threatened. The Union troops then withdrew across both forks to Guard Hill, where they made a stand until Confederate troops were able to get across the North Fork. Kenly made one last stand at Cedarville, but an attack by 250 Confederate cavalrymen shattered the Union position. Many of the Union soldiers were captured, but Banks was able to withdraw his main force to Winchester. Two days later, Jackson then drove Banks out of Winchester, and won two further victories in June. Jackson's campaign in the Shenandoah Valley had tied down 60,000 Union troops from joining the Peninsula campaign, and his men were able to join Robert E. Lee's Confederate force in time for the Seven Days battles.