The Confederacy had won some battle early on in the war, the biggest one being first Manassas or the battle of Bull Run, in july 1861.
The year 1862 opened like a nightmare for the Confederacy. The CSA lost its hold western Tennessee when Grant took forts Henry and Donelson, taking out a sizeable Confederate force, humiliating several inept Confederate commanders such as Pillow and Floyd, and paving the way for the loss of important cities such as Nashville and Memphis, and opening a huge part of the Mississippi for Union gunboats.
In the East McClellan had just dropped about 120,000 splendidly equipped troops on the flank of the Confederate capital, Richmond, Virginia. The important naval base of Norfolk was lost because of this, and the key eastern Confederate army under general Joseph E. Johnston had to retreat south to face this bold move (the only bold move McClellan would ever make). During this retreat huge amounts of supplies were lost.
Things looked pretty grim indeed all over the place.
The battle of Shiloh was one of many Confederate attempts to reverse its fortunes in the western theatre of the war. The CSA pulled troops from many different places, including New Orleans, for a heavy counterpunch. The goal was to take back the important area of western Tennessee.
Two Union armies were about to unite. One under Buell and one under Grant. A combined force of over 60,000 troops which would be in a good positition to conquer Corinth, Mississippi and move further south.
The CSA managed to assemble about 40,000 troops. On the 6th of April they attacked, before Buell had arrived. It’s a myth that the Union was taken completely by surprise by this attack, but it also hadn’t expected to be attacked with so much brute force. They knew the Confederates were in the area, but they couldn’t determine how many rebs were about to pounce on them. The Union wanted to avoid a confrontation until Buell arrived.
General Sherman, also present that day, later said this battle was the worst fighting he’d ever seen, in the entire war.
The first day was a success for the Confederates, they drove their enemies back, captured some of their camps, which they plundered, since many of them were starving. A part of the Union line reformed in what’s known as the Hornets’ nest. Union officer Prentiss usually gets the credit for organizing this defence, but that’s because he was the highest ranking Union officer to come out of the fight in the Hornets nest.
Then the Confederates were very unlucky (or perhaps very lucky!), they lost their commander. Albert Sidney Johnston was one of the few Civil War generals commanding an army that was killed on the field of battle. Although many generals commanding brigades, divisions or corps were killed or wounded it rarely happened that the general in command of the entire army was hit. For some reason the Confederates were more at risk, since out in the East commanding general Joseph E. Johnston (no relative of Albert) was grieveously wounded in the groin. It’s debatable if this was bad luck or good luck.
Joseph E. Johnston was replaced by Robert E. Lee who in about a month’s time completely rectified the situation in the east, and Albert S. Johnston was replaced by PGT Beauregard, a creole officer, who had ordered the first shots of the war, at Fort Sumpter, Charleston, nearly exactly a year earlier.
Upon taking command Beauregard called off the Confederate attacks on the 6th. He was in the rear and saw mainly stragglers and wounded soldiers and confusion. He thought he could drive Grant off the field or force him to surrender the next day. Many people blame Beauregard for throwing away a hard earned victory. However, it’s very unlikely a continued Confederate attack would have done any good. The Union had been driven into strong positions, was holding its line and had the support of two gunboats. Although it’s assumed that these were missing their targets, it was still a daunting force.
On the 7th the renewed Confederate attack went well at first, but then the Union counteratttacked, which made the Confederates fall back, to Corinth. A stubborn rear guard action by the military genius Nathan Bedford Forrest scared the Union off and they did not pursue the retreating Confederates in force.
The ferocity of this battle told Grant that the Confederacy was not going to go down without putting up a vicious fight. Before the battle he was thinking that the CSA would soon collapse.
The battle also lost the Confederates the vital port of New Orleans, because the CSA had stripped its defenses elsewhere to concentrate a large army in northern Mississippi.
Corinth fell later, without a battle, because the north moved up with a huge force, meticulously entrenching every step of the way and carefully avoiding being attacked again. Beauregard went on unauthorized sick leave and got replaced by the disciplinarian Braxton Bragg. However, the Union moved so slowly and cautiously, that the Confederates could execute a very bold move in the fall. They shifted their army and invaded eastern Kentucky.
The Union won the battle of Shiloh, but somehow managed to lose the strategic initiative, something they would manage repeatedly.
Combined losses for the battle amounted to 23,000 in killed, wounded, captured and missing. More than all the casualties from all the previous battles put together.