General A.S.Johnston had moved thither, after the evacuation of Bowling Green, Kentucky, and from all quarters the Rebels were assembling a vast army.

General Johnston became commander-in-chief on his arrival.
General Halleck, who then commanded the Western Department, ordered General Grant, after the capture of Forts Henry and Donelson, to move to Pittsburg Landing, and seize that point as a base against Corinth.
General Buell, with the Army of the Ohio, was ordered to join him from Nashville, and with other re-enforcements we would be ready to take the offensive.
Owing to the condition of the roads, General Buell moved very slowly, so that General Grant was in position at Pittsburg Landing several days before the former came up.

This was the situation at the beginning of April; Grant encamped on the bank of the Tennessee nearest the enemy, and Buell slowly approaching the opposite bank.

It was evidently the enemy's opportunity to strike his blow before our two armies should be united.
On the 4th of April, the Rebels prepared to move from Corinth to attack General Grant's camp, but, on account of rain, they delayed their advance till the morning of the 6th.

At daylight of the 6th our pickets were driven in, and were followed by the advance of the Rebel army.
The division whose camp was nearest to Corinth, and therefore the first to receive the onset of the enemy, was composed of the newest troops in the army.