Abraham Lincoln believed that the Civil War would be over in a few months, with the Union Army marching on Richmond by late 1861. The Union and the Confederate armies hastily assembled armies and Brig. Gen. Irvin McDowell led his unseasoned Union Army across Bull Run against the equally inexperienced Confederate Army of Brig. Gen. P. G. T. Beauregard. The Confederates won a surprise victory, particularly due to the efforts of Stonewall Jackson, and routed the Union. Both sides dug in their heels for a long war ahead.