After the 1861 Union defeat at nearby Bull Run, work on the Civil War Defenses of Washington proceeded in earnest. By 1864, the defenses were formidable, but mostly lay empty, as the fighting had moved south. In the summer of 1864, Confederate General Robert E. Lee secretly dispatched General Jubal Early and an army of more than 15,000 men up the Shenandoah Valley. From Harpers Ferry, engaging in battles or skirmishes (especially at Monocacy), they drove straight towards Northwest D.C. When they were detected there was a dramatic race to staff the defenses and save Washington.