Union armies were defeated at the first major battle of the Civil War, at Bull Run (Manassas) in Virginia. Any hopes for a swift Union victory in the Civil War were dashed at the first battle. After the surrender of Fort Sumter, two Union armies moved into northern Virginia. One, led by General Irvin McDowell, had about 35,000 men; the other, with about 18,000 men was led by General Robert Patterson. They were opposed by two Confederate armies, with about 31,000 troops, one led by General Joseph E. Johnston, another led by General Pierre G....