In March 1862, Major General Henry W. Halleck was put in command of all Federal forces in the Mississippi Valley, and he initiated a slow advance which he sent his two armies along the Tennessee River.  By early April Ulysses S. Grant had some 37,000 men near Shiloh Church and Pittsburg Landing, close to the Tennessee-Mississippi border, and off to the east Don Carlos Buell's 25,000 were on their way from Nashville to join him.  Meanwhile, Albert Sidney Johnston was desperately assembling all the Confederate troops he could find Corinth, Mississippi. He had more than Grant, but he would have to strike before Buell arrived.

The Union position was a reasonably strong one, but Grant and his division commanders felt it would be bad  for morale to have the men entrench.  General C.F. Smith told Grant, "By God, I want nothing better  than to have the Rebels ... attack us! We can whip them to hell.  Our men suppose we have come here to fight, and if we begin to spade, it will make them think we fear the enemy."  In the Federal camps a peach orchard was in glorious bloom, and war and killing seemed remote.

But just 25 miles to the south Johnston was pushing his raw levies onto the roads.  Like most of Grant's men, these Confederates were as green as grass.  They ambled along, whooping and shouting, firing their guns just to see if they would work, driving their officers into a frenzy.  P.G.T. Beauregard, second in command, urged that the attack be called off, but Johnston was adamant: "I would fight them if they were a million."  He ordered an assault for dawn on Sunday, April 6.

Grant was caught off guard, and in the first day's fight his army was almost pushed into the Tennessee River. It rallied just in time, Johnston was killed in action, and at dark Buell's troops began to arrive and one of Grant's divisions which had been delayed in reaching the field got to the scene.  On the second day the Federals reversed the tide, and by mid afternoon Beauregard had to admit defeat.  He drew his badly battered army back toward Corinth, and the Federals, equally battered, made no more than a gesture at pursuit.  The greatest battle ever fought on the American continent, up to date, was over.  The Federals had lost 13,000 men, the Confederates, 10,000.  The troops had fought with impressive valor, but they had been poorly handled, especially on the Union side.