After his capture of Fort Henry and Fort Donelson, General U. S. (“Unconditional Surrender”, for what he demanded of Donelson’s garrison) Grant was ordered by superiors in Washington to march on Corinth, an important Confederate rail junction. Grant moved about 40,000 men to the west bank of the Tennessee River, at Pittsburg Landing. Grant was then ordered to await reinforcements in the form of 30,000 more men under Don Carlos Buell. The last thing Grant expected was an attack by the Confederate troops under A. S. Johnston huddled miserably in the Corinth entrenchments.
Johnston realized that once the two Federal armies linked together nothing the Confederates could throw at them could stop them. Johnston boldly decided to throw his 50,000 raw recruits, (“fresh fish”) some without guns, at Grant’s army in a surprise attack. The attack was initially scheduled for April 5, 1862, but the muddy roads and inexperienced commanders made it impossible for the army to attack that day. In a roadside conference, most of Johnston’s generals, including Pierre G. T. Beauregard, said that the attack was no longer a surprise and so could no longer succeed because the troops had made so much noise (cheering, firing guns into the air to test them) on the march that Grant had do know about the “surprise.” Johnston replied, “I would attack them if they were a million.” The next day, the Confederate army smashed into Grant’s unprepared men in their bivouacs around Pittsburg Landing and a small church named Shiloh, Hebrew for “place of rest.”
The Confederates and the Federals engaged in fierce fighting at the inaccurately-name Shiloh Church throughout the morning. Further down the line, the Confederates were slowly grinding W. T. Sherman’s flank of the Union line through a peach orchard and the Hornet’s Nest, after which the Federals entrenched on a sunken road. Some Confederates stopped shooting to plunder the camps of the well-supplied Federals, giving Grant a chance. After a few hours, this strong defensive position was abandoned by Grant, who established a defensive line around Pittsburg Landing to protect it. As the first day of battle ended, this final defensive line by Grant held against the Confederates.
Grant’s position at dawn of the second day of battle was much better. The Confederates were exhausted after the first day of fighting. Grant, on the other hand, had received some of Buell’s men as reinforcements that night. In the morning, he decided to launch a counterattack. Grant’s newly-reinforced army slowly drove the Confederates back over the Union campgrounds they had lost the day before. By nightfall, the Confederates had begun a withdrawal back to Corinth.
Each army lost upwards of 10,000 men in the first real battle of the war (First Manassas doesn't count: it was more of a picnic than a battle). One of the Confederate casualties was Johnston himself, who was replaced by Beauregard. He was the highest-ranking Confederate killed in the war. The horror of Shiloh let both the Union and the Confederates realize that the war would be not only long, but also bloody. In the next few months, the two sides would engage in similarly apocalyptic and bloody battles that would finally result in defeat for the South.