The Union reorganized after Kernstown: McDowell's command became the Department of the Rappahannock, Banks's corps became the Department of the Shenandoah, while western Virginia (modern West Virginia) became the Mountain Department, commanded by Maj. Gen. John C. Frémont. All three commands, which reported directly to Washington, were ordered to remove Jackson's force as a threat to Washington. The Confederate authorities meanwhile detached Richard S. Ewell's division from Johnston's army and sent it to the Valley. Jackson, now reinforced to 17,000 men, decided to attack the Union forces individually rather than waiting for them to combine and overwhelm him, first concentrating on a column from the Mountain Department commanded by Robert Milroy. While marching on a devious route to mask his intentions, he was attacked by Milroy at the Battle of McDowell on May 8 but was able to repulse the Union army after severe fighting. Banks sent a division to reinforce Irvin McDowell's forces at Fredericksburg, leaving Banks only 8,000 troops, which he relocated to a strong position at Strasburg, Virginia.