The Battle of Shiloh: April 6-7, 1962.
A Confederate army of 40,000 men under General Albert S. Johnston surprised and attacked a Union army of 45,000 men under General Ulysses S. Grant. During the battle, which lasted from dawn to dusk and was one of the most desperate of the war, the Union troops were steadily driven back, but Johnston was killed, and his successor, General Pierre G. T. Beauregard, ordered operations suspended a few hours later. The following day Grant, with 25,000 reinforcements under General Don Carlos Buell, attacked the Confederates and forced them to withdraw to Corinth, Mississippi. Thus, Grant regained all the ground he had lost, and the two-day battle ended without a conclusive victory for either side. Casualties numbered more than 10,000 in each army. .
The Second Battle of Bull Run: August 29-30, 1862.
The Second Battle of Bull Run was fought on two days, August 29 and 30, 1862, near Bull Run. After failing to capture Richmond during the Peninsular Campaign, the North planned to unite the armies of General George Brinton McClellan and General John Pope for an assault on the city. By August 29, Pope, with about 35,000 men, had been driven north by a Confederate army of some 50,000 under General Robert E. Lee. Pope was facing Lee, whose forces were to the south, when Stonewall Jackson, with 23,000 troops, came eastward through Thoroughfare Gap and approached Pope's forces from the rear. The Union troops turned and, with Bull Run on their rear, faced Jackson's army. Jackson was speedily reinforced by Lee's troops and by a corps under General James Longstreet. Although the first day of the battle was inconclusive, on the second day Longstreet drove the Union army from the field. Pope retreated northward, was finally joined by McClellan, and then entered Washington. The Union loss was about 14,500; that of the Confederates about 9200. Lee, maintaining his offensive, then invaded Maryland.