This was a very daring thing to do. For with the Tennessee river behind him and with no means of easily crossing it in retreat, Grant must face the certain surrender of his army in case of an unsuccessful battle in that position. In such an event there could be no alternative. But it was not Grant's habit of mind to look for alternatives. He boldly took the risk as it was his custom to do. He threw his whole army across the river and there waited for the arrival of Buell's stronger force, which had been ordered by Halleck to join him and was marching in very leisurely fashion to do so. The army under Grant's own immediate command numbered now about 38,000 men, increased almost immediately to 45,000. That under Buell which was strolling westward to reinforce him numbered more than 40,000. He thus had prospect of an overwhelming force with which to assail the Confederates at Corinth, where under Beauregard's tireless activity they had succeeded in concentrating about 45,000 or 50,000 men, a large part of this force consisting of raw recruits unorganized, undrilled, undisciplined and extremely ill armed.
Whether Halleck planned this concentration of Grant's and Buell's armies for an advance upon Corinth as his partisans contend, or whether Grant planned it and Halleck merely accepted the plan as others stoutly assert, is a matter of no historical consequence, whatever biographical interest it may have. In either case the purpose of the concentration was to move upon Corinth in irresistible force, overthrow the Confederates there and seize upon the two important lines of railroad which intersect each other at that point. It was at any rate Halleck's purpose to command in this campaign in person. But it was not intended to advance upon Corinth until Grant's and Buell's armies should form a junction, and there was no thought or expectation that the Confederates would themselves assume the offensive. General Halleck planned to leave St. Louis not earlier than April 7, and perhaps several days later, for Pittsburg Landing. In the meanwhile General Grant had posted his army loosely and had thrown up no earthworks in the field. All his procedures indicated that he did not expect to be molested where he lay or to encounter the enemy until he should go in search of him. Indeed, he telegraphed Halleck on the fifth of April, the very day before the battle, saying, "The main force of the enemy is at Corinth, with troops at different points east.... I have scarcely the faintest idea of an attack (general one) being made upon us, but will be prepared should such a thing take place."
At the very moment when that dispatch was penned the Confederates with their entire strength were actually on march to assail an enemy who had "scarcely the faintest idea of an attack" being made upon him either then or later. In his memoirs General Grant said:
"When all reinforcements should have arrived I expected to take the initiative by marching on Corinth and had no expectation of needing fortifications.... The fact is I regarded the campaign we were engaged in as an offensive one and had no idea that the enemy would leave strong intrenchments to take the initiative when he knew he would be attacked where he was, if he remained."
It had been the purpose of General Johnston to deliver his blow on the morning of the fifth of April, overthrow Grant, and be prepared to fall upon Buell when he should arrive. But matters of detail went so far wrong that the Confederates, advancing from Corinth to attack, did not reach the neighborhood of Shiloh church, where Sherman was posted without fortifications, until nightfall of that day. They bivouacked very near the Federal lines, but strangely enough their presence in force was not discovered by the enemy they purposed to fall upon at daylight. In the meanwhile the head of Buell's column had come up and the rest of it was dangerously near at hand.
The Confederates made their assault with great impetuosity at dawn of April 6. The first that Sherman, who held the advance of Grant's position, knew of the impending battle was when the Confederates forty thousand strong rushed upon his camps and after a brief but stubborn struggle carried them, Sherman being driven back so hurriedly that he left his tents standing and the breakfasts of his men not yet cooked. The first that Grant knew of a tremendous attack of which he had had "scarcely the faintest idea," was when at his headquarters at Savannah several miles down the river he heard the guns at work at Shiloh.
There has been much and angry discussion of the question whether or not Grant and Sherman were "surprised," in the military acceptation of the term, by the Confederate onslaught at Shiloh. The point has little historical importance, but in the light of all the facts since disclosed by the records it is difficult to interpret what happened there otherwise than as a complete surprise, which but for the excellent discipline of the Federal troops and their superb fighting quality might easily have ended in disaster. We have seen that Halleck in St. Louis did not intend to leave for the front, where he expected to command in person, until the next day or even later. We have seen how confident Grant was in his belief that the Confederates intended no general attack either then or later and how he planned himself to take the offensive. It is certain that Grant's forces were not disposed as they would have been if an assault by the enemy had been anticipated. The several advance corps were posted with little or no reference to coöperation between them to resist an enemy assaulting in force. No line of battle had been formed or in any way provided for. Sherman, who was first assailed, was resting quietly in camps which would very certainly have been stripped for action if an attack had been expected. Indeed, Sherman's very latest reports to Grant had expressed the utmost confidence that no attack was in contemplation, and that the Confederates would do nothing more than annoy the pickets. He reported to Grant that they "will not press our pickets far." In brief it is obvious that neither Halleck at St. Louis, nor Grant at Savannah, Tennessee, nor Sherman, holding the front at Shiloh meeting house, anticipated a battle in front of Pittsburg Landing. They expected to fight on the offensive at Corinth when they should be ready to advance, but the thought of having to defend themselves against a Confederate force assailing them at Shiloh seems never to have occurred to them until the Confederates fell upon Sherman's camp with their "yell," for a first warning of their presence.
Sherman with two brigades lay in front. The two brigades were widely separated, as they would not have been had an attack in force been regarded as even a possibility. McClernand's division lay far in rear of Sherman. Prentiss, Hurlbut, W. H. L. Wallace and the commander of C. F. Smith's force—that general being ill—with their several divisions were scattered about in the rear all the way to Pittsburg Landing, while Lew Wallace with about five thousand men was posted several miles farther down the river in complete isolation from the rest of the force.
General Van Horne, writing under the direct inspiration of General George H. Thomas and with all the orders and dispatches under his eye, says that the several divisions "were widely separated and did not sustain such relations to each other that it was possible to form quickly a connected defensive line; they had no defenses and no designated line for defense in the event of a sudden attack, and there was no general on the field to take by special authority the command of the whole force in an emergency."
The ground in front of Pittsburg Landing was especially well adapted to defense. Flanked on either side by creeks difficult to cross, it compelled the assailants to depend almost entirely upon direct assault in front with little chance of success in any effort they might make to turn either flank.